Amazon has a cheap immersion blender. Most of the reviews are from soap makers. I love it! That and a cheap stainless steel bowl from Walmart did the trick for me.
EDIT: This is the one.
I have a Cuisinart which I got refurbished from Woot for $30. Here's the Amazon link for a new one. It includes a blender cup, small processor attachment and a whip attachment. Easy to clean and never stops working.
Cuisinart Smart Stick 2 Speed Hand Blender, Brushed Stainless Steel https://www.amazon.com/dp/B00AN9UJ68/ref=cm_sw_r_cp_api_F2Etyb3VDZDJF
Here is one on Amazon. Mine is like 20 years old lol, so I don't have a link to it. It's basically a hand held blender
I just picked this one up on Amazon. It was voted best by America’s Test Kitchen. I think it works great!
Braun MQ505 Multiquick Hand Blender, Black https://www.amazon.com/dp/B01EA5ZI2U/ref=cm_sw_r_cp_api_i_c4h3CbZFF0W5H
Just in case your goodwill blender doesn’t work out 🙂
For food processor, I went with the 14 cup stainless Cuisinart decades ago. As I did this, I cannot justify buying the new shiny Breville Sous Chef 16 Pro. As I bought it decades ago I expect it to last me the rest of my life. I have no idea how a modern Cuisinart lasts, I know their stick blenders always die 2 years into their 3 year warranty, that is when you find out that to get the warranty honored you have to pay shipping both directions which costs more than the stick blender on sale. My main uses are slicing and dicing after that I'd say puree. Wait I also like grating hash browns and cheese and sometimes veg for various things. Food processors are a great help.
If you can't get a Vitamix blender now, I'd go with a cheap Oster. Those Osters have always been very loud tanks for me. I'd get a https://www.amazon.com/Breville-BSB510XL-Control-Immersion-Blender/dp/B004RF7QJW before a Vitamix, you will get more use out of it most likely. Unlike the Cuisinart garbage stick blenders, the Breville endures all. The only thing I think is better is one of the big Warings (not the sell out garbage model Waring made as a cash grab) The garbage Waring lists one part number for their cheap commercial and that is for the whole unit, that means you cannot replace parts and that it is disposable. I'd give up my Vitamix blender before my Breville stick blender. The only complaint is its head is bigger than normal so it will not fit all the way to the bottom of a 32 oz glass.
Also remember: if you are strapped for cash, Craigslist is often much cheaper than black Friday.
When I make glaze test batches I use a cheap hand blender and run through sieve. Held up for weekly use past 8 years and still going strong. Use a spoon or a stick to get the lumps as small as possible and use the blender.
An immersion blender, especially with a whisk attachment, is very effective with any powdered meal replacement, and also easy to clean and store. I've had several years use out of this one but there are less expensive ones too.
This would be my suggestion as well. It will cover almost all of your requirements (not sure for the hardest nut butters), and takes up the least space which as you mentioned is at a premium. This one comes with a 3 cup processor and is well rated. If you are super keen on the nut butters you could also get a bullet type machine, which also have low profiles compared to a full blender or food processor
This is the America's Test Kitchen winner Braun Multiquick 5, it's about $65.
I picked up the Breville BSB510XL Control Grip Immersion Blender, Stainless Steel for $100 a few years ago. When I checked current prices, $150, seems too high.
I've got a KitchenAid one I paid $30 for. It's got a mini-food processor bowl, whisk attachment, as well as the blender blade, and came with a tall, deep mixing vessel that works great for things like dressings and sauces. I've been happy with it.
I'm not sure why Amazon wants $99. Mine was regularly $49 on sale 40% off at my local department store.
I think there's a few braun models. I'm pretty sure I have this one for the past couple of years.
I don't think I've yet run into a situation where it didn't do what I was expecting.
I bought this one: Mueller Ultra-Stick 500 Watt 9-Speed Powerful Immersion Multi-Purpose Hand Blender Heavy Duty Pure Copper Motor Brushed Stainless Steel Finish Include https://www.amazon.com/dp/B075X1KPLZ/ref=cm_sw_r_cp_apip_L194VQRTf7VC8
Storage is no problem. The grip/motor housing is about 7” long. There’s a detachable whisk head for whipping and a detachable blender head for puréeing. Both are about the same length, but not as thick. I use the whisk for protein drinks and have used the blender head for things like sauces and soups.
The whole thing fits easily in normal kitchen drawer; I keep the parts together a gallon-size ziploc bag.
I bought this guy in December 2019 and just barely starting to get old. We've made much Soap.
I'm presuming by ninja blender you mean one of their small countertop blenders meant for handling single portions, yeah? If so, an immersion blender is completely different and incredibly useful depending on what sort of cooking your wife does. An immersion blender lets you blend items while they are still in the pan, useful for making soups and the like. It's also a convenient way to make homemade mayo while not having to make a giant portion of it.
A bonus is if you get one with a few attachments such as this, you can also use it for when you need a food processor but don't want to lug out the full sized one. Honestly at this point, I almost never bring out my full sized blender, it's just in the back of the cupboard.
It really comes down to what cooking your wife does though. If she's really big on making smoothies and the like, an immersion blender frankly isn't up to the task for that.
that is probably your problem. you need a different blender for the cashews. try a stick blender. I use a Cuisinart and it works Great for me... I soak for 24 hours or at least an hour in boiling water. pour boiling water over the cashews and let set at least 1 hour. you also might need to add a little bit more liquid to allow the blender to move the bits around faster. but seriously try a stick blender.
this one is even more powerful than My Cuisinart. it should work great!
https://www.amazon.com/Mueller-Austria-Ultra-Stick-Multi-Purpose-Attachment/dp/B075X1KPLZ/
If you are getting into this on a regular basis, invest in an inexpensive immersion ('stick') blender, I have this one. Three seconds with the whisk attachment is all it takes to homogenize a blender bottle shake, and the whisk cleans up very easily.
Not the person you originally asked, but my gf bought me this one and it's been great. I've used it at least once a week for the past ~6 months. Still going strong. No complaints, would buy again!
https://www.amazon.com/Mueller-Austria-Ultra-Stick-Multi-Purpose-Attachment/dp/B075X1KPLZ
I don't know why the title on Amazon says "9 speeds" -- it's only has 2 speeds, regular & turbo, but it gets the job done for me. I use it to blend my tomato sauce, make fresh whipped cream, and whisk up large batches of eggs for frittatas or omelettes.
not sure the brand dave mentioned but i did end up pulling the trigger on one from amazon after listening to the episode and it does come out to $35.
https://www.amazon.com/dp/B075X1KPLZ/ref=cm_sw_r_cp_api_i_fI-pFbQPYVTGA
it came in on tuesday and i’ve had hella fun with it since. it’s perfect for my apartment where i don’t have too much space for an actual blender
Life advice: don't settle for "good enough" when buying something you will use every day. This Braun one is better than good enough, but see also the many related products Amazon helpfully shows further down the page.
you can use a potato masher but it will take a bit longer. have you looked at the stick blenders? they work great and don't take up much space and they are not overly expensive. I have this one
https://www.amazon.com/Cuisinart-CSB-75BC-Blender-Brushed-Chrome/dp/B00ARQVM5O/ref=sr_1_3?
This actually does a better job sometimes than my large ($200) Ninja.
I bought a year ago based on the America's Test Kitchen review. That page has an annoying sign-up overlay but if you click "read more" you can read the whole review including the name of the winner (on amazon).
lol gets most of the job done
One more vote for an immersion blender. I have this one, which has a little bowl attachment with a food processor-type blade. I’ve been very happy with it for both baby and nonbaby uses. https://www.amazon.com/Cuisinart-CSB-79-Blender-Brushed-Stainless/dp/B00AN9UJ68
I use one of these bad boys and I will never go back:
Pick up one of these when you can. It makes a big difference in consistency. Then add half a banana! You could try banana extract, but I have always just used actual banana. Hopefully somebody else has suggestions based on experience.
Use an immersion blender ( https://www.amazon.com/Cuisinart-CSB-75BC-Blender-Brushed-Chrome/dp/B00ARQVM5O/ ) and a big cup. No need to let it sit overnight.
Just be sure to rinse off the blender head after each use.
You can get them pretty cheap, there is not much reason to use one that is also used for food. I use this one and there are some more new ones even cheaper on Amazon: https://www.amazon.com/gp/product/B00TJTASYG/ref=oh_aui_search_detailpage?ie=UTF8&psc=1
I have this baby.
Comes with a small food processor that works great, and a cup, and a whisk. The best part is everything is insanely easy to clean. Also it's surprisingly powerful.