I just went through this with my '69 CS rear window. New, they're about twice as much as the front, probably supply and demand, but you can find good ones used if you're patient. I bought the rear window and sheet metal I needed from a guy parting out his CS, but have since bought a parts car myself. You're a little too far away to ship glass, otherwise I'd have them for you.
Keep searching, you'll find them...
Dan