Hi Piticli,
I don’t maintain a listing of all of the suppliers of memory foam toppers available, as that would be much too large of a task to maintain in an ever-changing environment. As you’ve probably already found, there is a list of some better suppliers of which I am aware in the topper post I linked to previously.
A 5 lb memory foam topper would be a good quality material. I would focus on something with a higher polymer density (not using a lot of scrap gel beads), something that is at least CertiPUR-US certified, and something that hasn’t been compressed for a long period of time in transport. You may also wish to get something with its own cover if you don’t have one already.
Phoenix