I've bought polycarbonate as thin as 0.010 to cover the outside of the robot with. That thin it comes in a roll. 48" wide by however long you want. It seemed like they called anything that was "rollable" film and stuff that shipped and stored flat "sheet".
Try to find a local plastics supplier that supplies to sign and screen printing shops if you are looking for large pieces of thinner film. If they don't have it, they can probably get it for you with their regular deliveries. Shipping will kill you if you have to buy it mail order.
I used to use Calsak Plastics when I lived in ATL, but they don't have a warehouse in your part of the country. Their website is
http://www.calsakplastics.com , at least you can look at a pretty wide range of what may be available. Wish they had a warehouse near here in MN. I'm still looking for a polycarbonate supplier here that will charge me less than retail

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