the most common pistol sold in the aquarium trade is Alpheus bellulus or the tiger pistol shrimp. This would be a good bet to pair with your shrimp goby. Keep in mind that there is no way to predict if they will find each other or not. Once paired, it is an amazing relationship to observe. As mentioned, the pistol has poor eye site and relies on the goby for protection and, in some cases, food. In return, the goby gets a nice tunnel to live in dug out by the bull-dozing pistol. When out in the open, the pistol will always keep one antenna on the goby at all times. If they can not feel the goby or have lost contact they will be back in the hole faster then you can blink. I have three peppermint shrimp, two skunks, one fire shrimp and various crabs in my tank and have had no trouble with my pistol.