Looking for alternative to Lexan sheets for DIY or crafting projects
You could try ABS plastic sheets. In 1/4 inch thick panels is it very rugged and quite rigid. ABS drills very nice as well. 

For a comparison look at these choices from Amazon:

ABS 12"x24"x0.236" Black - $12.20

LEXAN 12"x24"x0.250" Clear - $27.28