Where to get UV70 or Museum Glass or equivalent?

[Bartc]

Not sure where to post this question. Since getting deeply into pastels I have noted that only "white glass" (not regular "green glass") that is non-glare will do. I care less about the UV blocking, but it seems that's the way it comes, like "Museum Glass" and "UV70" or the Groglass equivalent.
Does anyone have a source of such glass already cut to sizes that is reasonable? Pretty expensive to use a framer each time!
Thanks.