Only one that i like is the comfort with extended memory foam pillowtop its been grest for my husband and i (we both have fibro).

Google foam mattress. Not the topper but the entire mattress is layered in different foam. You can choose the thickness and the amount of firmness. They're varied in price. Don't get caught up in the higher priced one till you see if it's the type you like. I'm happy with mine. Doesn't feel like sleeping on river rocks.

something like that :) https://www.amazon.com/Best-Price-Mattress-4-In...

I think you should buy a top mattress memory foam it doesn't cost a lot, plus you have a 1 month or so free trial if it doesn't fit

You used to be able to buy foam for the mattress at places like Walmart. Almost the same as what they call the egg crates but no bumps and they came in 1" , 2" or 3" thickness.
Putting that on top of the mattress does make for a much nicer sleep at what you can afford.