Windshield gasket?

Where do you guys get yours? I need one for my latest project (not an A body), a 1977 Plymouth Trailduster. I've got the info that any windshield up to '92 will fit. I've got one out of a '87 truck. The glass thickness changes after a point, so you need the gasket to match. Where do you guys get yours? (I said that already)
Thanks, mike