Well, the quest has ended- with the arrival of a second rear wheel (finally).
Just to provide some pricing guidance:
I acquired two rear wheels from two different sellers- both board members, BTW- both were unused, never even had a tire mounted. One cost $320 shipped, the other $395 shipped.
In the middle of the arrival of these two was one purchased on fleabay for $375 shipped that was sent to me in the BMW box and arrived damaged. (Rim chipped.) UPS denied the claim ("inadequate packaging"), now it is up to AMEX and paypal to figure it out...
So, just fyi on the 'going rate' for new, never mounted rears!