Hi There,
I am not sure where you would get it in the US/EU, but from what I read on Audio Asylum you should be able to easily order it on the net. Here things are slightly harder to come by, so I had to go to an industrial manufacturer of numerous types of rubbers and foams and get the PE Foam from them. Wasn't that difficult really - yellow pages, 2 minute phone call and that's it. I even got it for free :) cause they normally come in a huge board of around 5mx10m but I only needed two small pieces so they gave me offcuts they were gonna throw away anyway.
I am not sure where you would get it in the US/EU, but from what I read on Audio Asylum you should be able to easily order it on the net. Here things are slightly harder to come by, so I had to go to an industrial manufacturer of numerous types of rubbers and foams and get the PE Foam from them. Wasn't that difficult really - yellow pages, 2 minute phone call and that's it. I even got it for free :) cause they normally come in a huge board of around 5mx10m but I only needed two small pieces so they gave me offcuts they were gonna throw away anyway.