I have an idea for a very specific project that would involve a custom GBC screen cover. Since I'm not a fan of painting on the outside of the screen, I'd have to use a clear screen cover and put something underneath it. Unsurprisingly, there are no clear GBC screen covers (that I can find). I'm assuming I'll have to cut one out myself, which seems easy enough using the old one as a template and doing some careful x-acto knife work. This leads to my main question.
Where would I find hard clear plastic of the right thickness for a screen cover? I'm not going to order some custom stock from halfway across the world for an exact match, so readily available substitutes would be good.