Your local auto glass company should be able to get you a new one. '63-6 A-body all models will work. If you're in SoCal, you can come by my place and buy one with a wiper scratch, rock chip, or fog in the corners if you just need one to fill the hole and make the car legal! I won't ship one so please don't ask.....they're too fragile for the packaging materials I have.
Thanks, Mark