Jon,
Last fall, we were shopping for plexiglass to build a cockpit
console and found both Lexan (polycarbonate) and plexiglass (acrylic,
polymethyl methacrylate) at HomeDepot. If it was not on the shell,
they may order it for you.
Aircraftspruce also sells Lexan
http://www.aircraftspruce.com/catalog/mepages/lexan.php