M&P9C. Holds 12 rounds. But can also use the larger 17 round mags as its big brother the M&P9. The M&P9C is not much bigger than my G42. Just wider. And it does fit in a pocket, just not as well as my G42.
my G42, you can get 10 round mags for it and I think I’ve seen 12s. Factory is 6. You can swap the base plate and get two more without much add on to the mag.