This weapon is available as community-made addon uploaded to Steam Workshop. It adds new weapon to the game. Pistol model itself made by me. Textured by 4Echo. Full list of creators is available in the description on the description webpage.
Also available for Left 4 Dead 2 game.
Link(Click Subscribe to download):
http://steamcommunity.com/sharedfiles/filedetails/?id=519678919 - Garry's Mod
http://steamcommunity.com/sharedfiles/filedetails/?id=676433429 - Left 4 Dead 2
http://steamcommunity.com/sharedfiles/filedetails/?id=635235720 - Left 4 Dead 2(with accessories)