Oooo hey Gary - I've seen and discussed stuff like this before so maybe I can lead you to some other sites that have similar-ish materials.
Again the shrinky material I looked into came from a company that also made "Expand It" .. pink house studios (can't find it off the bat but Try "reduce + expand + Pink House" in a google search maybe?) Similar looking stuff.
Also, I thought of some of those sponge like materials that you can buy in a dime store that are little 1" long sponges that soak up water ... NO IDEA what that material is called (beyond extreme sponges...
) but they seem to be similar in concept with a different material that I think stays expanded (well the one I've seen was dry and big later).
Some leads I hope!