As far as I know there hasnt been any 'surplus' government owned M9s sold on the market, but this has happened in the past with .38s, 1911s, and others. However you do find massive lots of magazines (used and new), grips, and components at DRMO auctions from time to time...just not frames or complete guns.
Now Beretta USA will sell you a dead ringer M92A1 which is about 99% the same thing
http://www.berettausa.com/products/model-92a1/
It just isnt 100% the same thing. (No US Property markings, etc)