I've seen on a few sites people talking about getting their glass from Bob's Classic Auto Glass listed below in vendors section. It use to be any decent glass company would cut lamintated flat glass for you if you brought them the pattern or old glass. Think that is another lost art coming soon as the old guy's retire.
We use to use an old guy that opperated out of a small 15x15 shed. Dad said he had almost all glass patterns from the early 1900s up. Everytime i would call him, i would ask if he had that pattern, he always answerd Yes i do😁 Had him cut some custom sizes, he just said bring me a pattern. His edges were alway nice and smooth. Always reasonabley priced, cheap actually.
We use to replace school bus flat winshields, if they weren't broke to bad i would sa ve them for my projects, vent window, side glass. Dad showed me how to cut glass so between him and watching that old man, i did a fair job.