I am working on this DIY project that would mold a super soft foam ball with a plastic core. I have tried polyurethane foam at 3lb/cf (sold by by Foam-it) but it came out still too stiff. After doing some research and comparing different materials, it appears that the polyester sponge (same as dish washing sponge) would fit my needs. However, I could not find any online stores that sell the polyester foam making compound in small quantity. Anybody could point me to the right direction?