Saw Tom's post after i measured this so i hope he checks my measurements. The mag plug is 5/8 and appears to be a 28 thread pitch which is non standard. MSC has one listed (old catalog price about $30). Checking the bore of the body it is close enough to the correct drill size for 5/8-18 this should be available at a local hardware store for less than $6. The problem with using a standard size is finding a pretty bolt that will suit your purpose. The closest thing i can think of is a socket head cap screw, but the head is still going to be bigger than the body of your mag. You can also take a scrap of aluminum and turn it down the way Tom suggested and die cut threads on the end, but this will be time consuming and you will have to spend more money on tools, which isn't always a bad thing. Let us know what you decide to do. HTH