Check the restoration catalogs for them, just don't look for C-body applications. Check the more popular B/E-body applications and match the diameters and such of what you need. Sometimes, an item that was more generic would be used over several body platforms, just that the B/E-body people might not know they might have been used on C-bodies, too. OR in model years they might not service, too.
Just ask for the dimensions (ID, OD, width, etc.) and see if they might match what you need. Might ask them to email you some pictures of what they have. Or even order one of each, if they are not too expensive? Then go from there.
Seems like the old Gary Goers catalog had some of those things in it?
Just some thoughts,
CBODY67