After Really Right Stuff now Arca Swiss announced a new L-bracket that, among others, will also fit a Leica M9 rangefinder. The price will be 190 Euros. The original info is in French but Arca Swiss confirmed compatibility with M8/M9:
“Thank you for your message, our design department will send you a simulation of your Leica M9 with L-brakets ARCA-SWISS. We confirm that our L-brakets fit your device (and also with the M8).”