check your local yellow pages for plastics suppliers.
if you can't find acrylic, you may be able to find some 1/4" thick polycarbonate scraps.
just be careful - PC does not like a lot of solvents.
If you have absolutely no luck on your end, PM me and I'll pick some up the next time I'm in Wichita. (there's an aircraft manufacturing salvage yard - callet "The Yard Store" - all sorts of cool materials laying around)