I believe that Tony Branda (
www.cobranda.com) stocks them, but they're pretty expensive. Unfortunately, I hate their website interface and can never find what I want on there. Otherwise I would tell you for sure. If memory serves, they were about $100 -- unpainted I think. The trim piece that you refer to (what the pedestals bolt to) is a standard '68 Mustang part, with the interior part painted the GT/CS Dark Grey Metallic.
Funny you should bring this up now -- I was just thinking about this very topic this weekend. My car is missing the pedestals, too, and I know that I can make them for less money than Branda sells them for. I have Paul's books, so I can get the correct paint and I can make them to the correct specs. I am planning on doing this for myself. If all goes well, I would offer this service to my fellow GT/CSers at a very fair price ;D.
I'm going to set up a poll in the Classifieds section to see what kind of interest there is for this.
-Winston