The one in the movie was riveted to the leather panel on the pants. That is how I have attached them.
The Three upright pieces for the clip. the two side by side are the actual clip, the one at the bottom supports the base of the trigger guard. The Clips themselves are VERY stiff. I would recommend maybe drilling through the backside and putting some screws in them to reinforce them - as I would be worried they may snap.
This was designed to work with the NERF blasters - not any other model.