hope you find some, When I first read your thread I was wondering why you didn't just google mags for sale. I ordered i think 4 12 rounds for my 6906 from CDNN about 4 years ago. I can't believe they are this hard to find now, but I guess they are, after googling them I couldn't find them except on GBroker. You may want to try the Smith and Wesson Forum.
Love my 6906 what a cool carry gun.