Want to Buy contact screens (halftone), opaque

I am looking for replacement contact screens for creating halftones on my process camera. Had no idea how rare these things had become! I also need any jars of old Kodak opaque that anyone might have around. If anyone has any leads on these items, please let me know.
Thanks.
Jack
(specifically, I need at least 100 dpi, larger than 11x17. Megentas' okay. Positive, or negative. a set of color seps would be fantastic. I really don't want to have to invest a couple of $k into going digital for my seperations when I allready have analog gear-minus all the screens. Make sense?)

Jack,
Size, Screen ruling, color/angle needed? I can check with a few friends, I only have a 20x24 133 lpi magenta sep contact screen left myself.

any and all. Would love to have a full set of color seps, but any will do me good.