Clear, sturdy building material for stage props...?

Question:I am looking for a clear and sturdy (and preferably relatively inexpensive) building material for a stage prop. I am trying to imitate glass or plastic block (just can't afford it) so clear is a must! It will be placed in a wooden frame and must be 54" x 54" or combined to get said dimensions. It must be able to be drilled or somehow have 4 wooden shadow boxes weighing apx 3 pounds each on it and not need too much back support so it can be backlit. Basically. I am reconstructing the control pannel as seen in The Rocky Horror Picture Show... I've considered plexiglass, polycarbonate, twinwall polycarbonate, Solexx... I really like the Twinwall, but there isn't a retailer close (I'm in Ohio) and definently can't afford to ship it here at min $250. Ideas??

Answers:
Try clear acetate (sp). It's a thin, but flexable material that art stores sell.. Or clear mylar, or that heat seal stuff like you use on windows in the winter... Good luck.