Don't be discouraged. (OK to be frustrated) Hippo has offered a lot of good ways to get your hands on the real stuff. Living in Slick Rock, Idaho I too had a devil of a time finding fanfold. Ended up with the green stuff. Just to get going, I bought sturdyboard from Wallyworld at 2.00 a sheet. Getting the paper off wasn't too bad, but the foam has very little strength. I compensated by using Kevlar thread, anywhere from 3-7 strands glued to the LE and TE, or any place else I thought needed strengthening. Is this the perfect answer? No. But it does allow you to cut out parts and get a plane built while you search for the Holy Grail. You can find kevlar thread at an archery shop, or fishing tackle outlet. Carbon fiber tape or tow could even be found at your LHS if you're lucky. I've even used polyester thread from the fabric store, although it stretches more than kevlar. It's amazing what desperation can do!
Don't take NO for an answer. By all means, check out the offerings at www.foamfly.com.
When Dan gets the big guide out there is going to be a lot more foam in the air!