Hi LookingNow,
The component list here includes the better online sources for polyfoam that I’m aware of. There are also some comments and comparisons in post #4 here and post #6 here that may be helpful as well.
I don’t have a list of local polyfoam suppliers in Massachusetts so you would need to do some google searching but it may be worth calling https://www.yelp.com/biz/bonnie-foam-rubber-and-products-allston in Allston (although their website is gone so they may no longer be in business).
Phoenix