While shopping for a new wiper blade for my wife's car I found a Bosch Steel Tech wiper and bought it immediately, not for the wiper but for the container. It's a somewhat heavy, fairly rigid plastic measuring about .012 thick. Part of the plastic is covered with paper but there is still a good sized area of clear plastic that will make good window material. I found it at WalMart but I'm sure it's also available at most automotive supply stores.

I suppose one of these days I should also replace the wiper in my wife's car.

Tom

I use old architects' drawings....The ones drawn on a (once) clear sheet of acetate, then used to make blueprints. They've yellowed to the point of a dirty look.
For the amount I use, I must have three lifetimes' worth of window material....

I saved all the clear plastic from many containers, from headphone cases, window shades, etc. theres a lot of clear plastic packages now a days

DPM always has extra in their kits. I also use the packaging on Atlas turnouts.

Just be careful, I used to salvage clear plastic from containers until I found out some of them may yellowish over the time.

Matt