What I'm guessing is they are the pup covers and edge or dallas or somebody cut out the rings to make them that way. I really don't know. I am actually in search of these too.
I found a store in the UK, don't have the link any more, but they were not that helpful anyway... There must be another source. Surely some of you have access to the yahoo news groups etc... and can find a thread on the forums of sites etc to see.