The good foam is called High Resiliance Foam. You can get it from foam stores that custom cut foam for reupholstery or custom upholstery. If you get it in 4" or less layers you can even roll it up or fold it if you need to transport it (although the layers do move independently and can be a bit of a pain, although two layers lets you get a harder bottom layer and softer top layer). It is expensive but less than the really expensive mattresses (e.g. 8" of king size via 2 twin XL size would be under $900 from where I purchased mine a couple of years ago, I'm not sure if they could do king or queen size as a single piece).
As someone who has trouble sleeping I've found what I sleep on seems to make surprisingly little difference as long as it isn't causing pain. Also, the breathable thing is likely a difference between cold sleepers and warm sleepers; as a cold sleeper I use a waterproofing layer and prefer that to a breathable mattress.
As someone who has trouble sleeping I've found what I sleep on seems to make surprisingly little difference as long as it isn't causing pain. Also, the breathable thing is likely a difference between cold sleepers and warm sleepers; as a cold sleeper I use a waterproofing layer and prefer that to a breathable mattress.