Please welcome Eyoyo Underwater Fishing Cameras.https://amzn.to/3siEgXn
When we replaced the foam in our popup camper beds we used this.https://www.walmart.com/ip/Spa-Sensations-4-Memory-Foam-Mattress-Topper-Multiple-Sizes-with-Theratouch/4569413Its just a 4" mattress topper, but it is pretty comfortable to sleep on, just had to cut to size and reused the old mattress covers. It was also quite a bit cheaper than regular foam from craft stores around here. Im sure you can find cheaper toppers out there, looks like the price qent up a bit from when I bought mine.