Lowes will cut acrylic for free, but acrylic will probably warp pretty quickly.
You might try a window repairman or window repair store to see if they'd be willing to cut a scrap to size for you- possibly could get it done more cheaply than at a glass store for something this small.
fishman333 - Check out POP Display's ebay store. Look at Lexan Sheets
in 1/4" or 3/8" thickness. I've bought several time from that seller fast & friendly. He'll make a few straight cuts for free.
Lexan is used as bullet-resistant glass (nothing is truely bullet proof).
I've made wet dry filters out of Lexan. Last spring I made a battery tray for my Scion to install an Optima Battery.
You can cut it with a jigsaw, drill it no problem. If you want to get creative you can polish unfinished edges with sand paper. You would work from saw 100,150,200,400 them out over 1000 depending on what you want in a finished top.