Re: what about a S&W 3913?
I have both a 3913 and the 39-2, and I ran a 6906 pretty much into the ground. The 3913 is a great summer carry piece, and I wouldn't worry for a second about the extra width of its ambidextrous safety. FWIW, at least a few Federal IGs that I know of were issuing them in the 90s, so they may yet come onto the market as "shot little, carried a lot" surplus treasures. Probably the best aftermarket accessory is a Hogue rubber grip panel set