I have been searching for trim rings for 1970 Z-28 wheels for a while now. According to Camaro Specialties, the only company who reproduces them, has had them on back order for 7 months. Weeks past and still no trim rings. I then stumbled across this company. DR Automotive. The website is below. Hope this helps some people.
-Dan
http://www.drclassic.com/index.html