I'm not sure if anyone makes a longer mag for the Nano, though in my opinion it would be a little pointless. The upside to super-small single-stack 9mms is that they're super-concealable. Once you extend the grip length to accommodate your pinky you're extending one of the most important dimensions in a handgun's concealability. At that point you might as well go with one of the bigger sub-compacts that are easier to shoot, like the PPS or Sheild.
0331: "Accuracy by volume."