I reworked my replica year 2 & 3 laser pistol after examining photos of the real one and freeze-framing images on the DVDs. I discovered there's a brass ring that holds the clear end cap in place. Also there's a silver trigger that protrudes from what I originally thought was the actual trigger. I made the handle removable to replace the 9 volt battery, but the original had a plate in the back that could be removed to gain access. I could see a screw in one of the shots on the DVD.

 
MY ORIGINAL AND LESS ACCURATE REPLICA

THE ORIGINAL LASER

Never fire a laser pistol in your home, as I have now learned.
But seriously folks...
This project took a few weeks of spare time. I had no plans to go by, but found several photos to use as a guide. I incorporated a momentary switch, an LED and a 9 volt battery to make it "work". The next trick is to devise a way for the robot to hold it.