[C10 - C90 Bill]

For a new one, I would start with your local Auto Glass Dealer. There are probably some new ones still out there and maybe they could track one down for you. For a used one, although a little rare, there should still be 100's out there. Try some big truck salvage yards. I would check on the interchange to be sure, but any 5500 to 7500 of your cab style should work.