Garrett Pro-Pointer (first gen) retainer ring

This adds a secure hole to the Garrett Pro-Pointer (first gen) which was included in future Pro-Pointer revisions. I tested another version (Not the linked one but looks the same design) but it was too loose and flimsy so I decided to design a different style. I tried for the lowest profile with keeping up the strength of the ring and hole. It is slightly threaded to fit over the threads snuggly, and is best put on without the o-ring and then add it back on when completed. I just wanted to s