I seem to recall someone looking for brass rings for their alembic pickups. This may be one to start with.
I think Keavin was involved in the thread but I don't think he was looking as these would not match the shape of his alembic pickups.
 
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=280142606425&ssPageName=ADME:B:SS:UK:1
jazzyvee

That's a pickup ring from the bridge pickup of a Yamaha BB3000S or similar.
 
For example:
 

Someone is telling porky pies on their listing it seems....
Jazzyvee