I am not an expert, but I think the hammeress version was a 940, and the 6 shot with a 3inch barrel was a 547. I have been looking for the 547 for a while.
There was a 940 for sale on ths forum, and I think there is one currently on Calguns.net.
Also you might look at:
http://froogle.gunbroker.com/Auction/Vi ... m=42034631
Not my gun, and more than I want to pay.
Also Ruger made a SP101 in 9mm that used moon clips.
Lastly, there is a French Revolver that takes multiple cylinders (9mm and 38), but I have no idea if they ever made it to the US!
Good luck
Richard