What youre gonna wanna do is get yourself some Calcium no D3 for the daily dusting. Get some Calcium w/ D3 for every other sunday and multivitamin to go every 2 weeks as well. I do calcium no d3 mon-fri plain un-dusted crickets on sat and on sunday i alternate between multivitamin and calcium with d3. It will keep your little guys nice and strong. Release the crickets into their cage for them to naturally hunt and get some cardio in ;)
These are the ones that i use
https://www.petco.com/shop/en/petcostore/product/zoo-med-reptivite-reptile-vitamins-95095
https://www.amazon.com/Zoo-Med-Calcium-Without-Vitamin/dp/B005FTMGYO
https://www.thebiodude.com/products/repashy-calcium-plus-3-oz-jar
You probably have to order from different companys.
Aslo the repashy is for a variety because sometimes leos will get bored by there supplements.
for inside their tank, you want a supply of repti calcium WITHOUT d3: https://www.amazon.com/gp/product/B005FTMGYO/ref=ppx_yo_dt_b_search_asin_image?ie=UTF8&psc=1
then for dusting their insects, you can either rotate multivitamins and repti calcium WITH d3, or just use an all in one every day. this is what i dust with daily: https://www.amazon.com/gp/product/B0844ZD85V/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
I ordered mine off amazon. My leos actually really like it too! I’m always refilling their little calcium dishes.
How many crickets per day? You should supplement what the crickets are eating by dusting them with calcium powder when you feed them to the chameleon. This is a well reviewed calcium supplement without vitamin d3. You will want to give him calcium with vitamin D3 a couple times a month. Here is an example of that.
Calcium helps with muscle control and a deficiency could be contributing to your chameleon's prolapse.
You don't really need a block. Most people use the calcium powder (Also look into versions without vitamin D3, buy both with and without) that you can find at nearly any store. Pet stores certainly will have it, but WalMart near my house has it as well, even though the reptile/fish selection is limited to one half an aisle. Also put some of the calcium without D3 in a little dish (I use a milk jug lid) and they'll take part if they feel like they need more calcium.
Calcium Without D3:
Calcium With D3:
Add-On Item (Cheaper but a lot smaller)
Also look into a separate vitamin.
This will give you the options necessary for size and with/without D3.