We replaced our original with the following: Sam’s Club 8” Night Therapy Total Comfort Premium Memory Foam Mattress-Queen item 186150.
We've been using it since 9/2012 and prefer it to a sleep number that we had in the house. We now have replaced the sleep number mattress with the same 186150 in 2018.
Points to note: flexible and easy to move, about $250 with shipping so it doesn't break the bank, length can be cut down with a serrated knife if you have a short queen in the RV, no partner interference while sleeping, no electricity needed so it's great for boondocking. It does get a bit firmer when cold (30-40 degrees) but not an issue. I weigh 235 lbs.
Good luck with whatever you choose.