Went to a local shop in Olean, NY..one of those honest "factory outlets" where the manufacturer actually runs the store.
I looked at their foam (all 4")..there were 4 grades. I picked the next to the firmest density...it felt just right and the store manager recommended it, since he has served many RV people..
Nice about going to a true "factory store"..I needed a custom size 48"X72"....
No problem, he will have it for me on Wednesday..covered as a regular mattress in a biege cloth cover..
..The price..$79.00 + NY state tax..
This is a family owned & operated business in Jamestown (far western) NY..and they have stores in western NY & Penna..
Since they have a website..I presume they will ship !
If you are reasonably nearby...or want to find your nearest store phone..
(716) 665-2247 Fax (716) 665-4037