I just ordered some high density seat foam on Amazon and got some marine/boat vinyl from a fabric store so that it’d be waterproof. Worked like a charm on my 2 seater that we take on super rocky terrain.
Might have to build it yourself. I built all my own beds out of plywood, 2x2's and 4" foam for the mattress. One of the beds is a murphy bed, and for that I had to order plans and hardware (which I modified), but googling :murphy bed plans" might be another avenue to search or at least get ideas.
Not as pretty, but memory foam works well too. Upholster it if you want (or toss some pillowcases on, cut it to size and stack however much you want/need https://www.amazon.com/FoamTouch-Upholstery-Foam-Density-Cushion/dp/B00TSVSA7C/ref=sr_1_4?dchild=1&keywords=memory+foam&qid=1595013597&sr=8-4
If you wanted to replace the foam (not sure if it's bad -- but could also make thicker and sturdier), I recommend looking for "rebonded foam". I previously made a DIY bench cushion and bought 2-inch-thick "high density upholstery foam", but it's not as dense as I'd like (ok for my general purposes, as I have other real weight benches). If you're going to replace the pad cover yourself, I do recommend figuring out how to sew it properly. I hacked my way through "gift wrapping" the edges and looks not as clean as it could, if I had done more research and cut different pieces (?) and sewed it up.
Which closed foam mattress?
How much R do you get from the memory foam?
Down to what temps have you used this combination?
How much does the memory foam weigh after you've cut it?
This 2" memory foam pad weighs 3.7 lbs (pretty heavy):
https://www.amazon.com/FoamTouch-Upholstery-Foam-Density-Cushion/dp/B00TSVSA7C/ref=sr_1_4
Most of the tutorials I know of are purely makeup tutorials, but every queen dresses differently.
I'd say these are the big requirements:
-Wig (preferably a big one). Go to a wig store and buy a decent one (I'd start with something like this or this (lace-fronts are usually the best).
-Dance tights (some queens wear up to 5 or 6 tights at a time - this helps shape your body more like a female's because it covers the padding).
-Padding: get a piece of thick foam (something like this) and use either a safety blade or an electric turkey/meat carver to saw out something like the shape of an inverted comma (for your hips). The leggings/tights will cover this up.
-Padded bra (or fake breasts) - remember to contour (and obviously shave) your chest to outline your breast areas (if they're going to be showing)
-Fake/costume jewelry - silver or gold, pick one and stick with it for any one particular outfit. I'm not sure where you're located, but everyone in Los Angeles goes to Santee Alley to get their costume jewelry, but I'm sure there are a million places online to get them too (Etsy, for instance).
-Heels. You'll probably want to start with 4-inch or less if you've never walked in them before. Practice walking in them a lot. A huge telltale sign that a queen is new is when they're all done up, but they're half slumped-over walking because they can't properly walk in heels.
I'd say that your first step should be to go get a pair of heels and practice walking in them. I see people out in West Hollywood on a daily basis dressed completely as a man, but wearing heels to practice. It's not as easy as it might look, especially for a guy.
Unfortunately, drag isn't a cheap hobby (or career). If you don't have a bunch of money to throw at it, go bargain-basement hunting online. The good news is that most places will put large sized shoes on sale, since they're harder to sell.
Most new queens start out with a corset-based outfit, but it's not a requirement. If you're a bigger guy, it might help shape you closer to a woman's body type.
Hope that helps! (This advice is from the husband of a drag queen, so it's second-hand, but if you have specific questions, I'll be happy to ask my husband for more info).