Have you checked out Triton Gallery - broadwayposters.com for the window cards? If they still have the originals they usually go for around $25. If they are reproduced they're usually around $75. Triton also has a small selection of playbills in their store in NYC. It's hard to know exactly what's there, but you might get lucky!
Yes I have tried Triton. The cards I am looking for can only be bought from Triton as repro's. I would prefer originals. As I said in my original post I am eager and willing to pay a fair price