Raven, Birkin's Triple Shot appears to be an unholy amalgam of a Beretta M93R, Springfield XD and the Sig P220 SL Sport. Honestly, unless you can get someone to cast the slide of a P220, with the hammer, rear, trigger and foregrip of the 3R with the frame of an XD, just stick with your standard cheapo airsoft gun. I usually don't tell people to buy cheapo airsoft, but with Resident Evil 6, most of the firearms are all two or three weapons combined. Take the "Bear Commander" for example. Some argue that it's based on the FN FAL paratrooper variant, but if one looks closely, the weapon is chambered in 5.56, while the FAL is chambered in 7.62, and certain parts of it look closer to what one would imagine a Chinese knockoff of an H&K G36 to look like.
So, yeah... best bet is to get a Glock 17 or Beretta M9 holster, leave the holster empty and grab yourself one of those cheap Remington 870 airsofts with the weaver rails on top for a holo sight.
Whale cancer! Eff yeah!