I've got one pair of NOS vent covers (part #'s 23 and 24 it looks like) but I'm keeping them. I have a few used pairs of the same I pulled from donor's if you need a pair. They aren't cracked (one is painted however). I have no idea what they may be worth, but I'm flexible, especially to help a PY board member with one of these red-headed stepchildren.
As far as the solenoid assembly goes, I believe it is the same configuration as used on the '74 GTO (and possibly the early 70's ram-air Trans-Am's).