They were discontinued, by Chrysler, some time ago. However, I did some checking, and they are available from Moser Engineering ( http://www.moserengineering.com ) as part number 838TK.
Thanks. It looks like they use a tee bolt. Perhaps I can source them locally although I don't know how common those are. The Moser stuff will take forever to get. I see Dr. Diff has the proper bolts but it'll take a couple of weeks to get them from him too. Perhaps I'll just use std UNF bolts and grind a flat on them and tack them in place.