The popularity of the P365 micro-compact has all but mandated an entire after-market industry of SIG P365 accessories and P365 upgrades. Here are a few for you to consider.
The Colt Monitor (R80 Machine Rifle) was a modified BAR (Browning Automatic Rifle) adopted by the FBI and other law enforcement agencies.
Magpul Glock mags are available now for a number of different pistol frames, in a variety of capacities. Here’s some info and Magpul Glock mag reviews.