Beretta has offered the M9 as a special edition, but I'm not sure it is readily available. You might want to try Auction Arms or Gun Broker.
The only differences between the 92FS and the M9 are the rear sight (two-dot versus Sig-style bar) and slide markings. The M9 also has additional military part numbers on the slide and frame.
I've heard that the M9A1 has been purchased by some US military entities, but I'm not sure. That model simply adds an accessory rail to the frame.