Try ECS. I think they offer it and you can get it correctly date coded. I know they offer B Body glass, if they have the rear for the RR it will probably be the best available judging from their other products.
talked to AMD yesterday and after asking if they had any problems with the back glass fitting correctly they said that they smashed all the 68-70 rear windows they had and put them in dumpster. what does that tell yeh about the off shore glass.