Polycarbonate windows

Poly scratches too easily for a windshield on a street car, wipers will wreak havoc on it. Keep this in mind if you decide to have roll up side windows, they will scratch on the window guides. Also, your Scamp doors do not have full window frames so you may need to brace the poly as it is more flexible than glass and will tend to push out at speed.
I plan on poly side windows on my 65 Belvedere, but it is a post car and has full frames around the windows making things a lot easier for me. The rear windows will be fixed in place (no regulators). I am still on the fence about making the front windows functional.
You can get poly at places like Lowes, Home Depot, etc. It is used for door 'glass' replacement. Not certain if these are the best sources, but it is a start.