I am happy to see that holsters for the Nano are beginning to appear. Some I have found are, in no particular order,
Beretta Nano | PJ Holster LLC
Holsters by RGrizzle
Gun Leather, Concealment and Cowboy holsters, Azle, TX.
TT GunLeather High Quality Leather Gun Holsters
Custom Concealed Ankle Gun Holsters Ammo Pack Chicago Screw Razor
Custom Holsters by Ed Buffaloe
I'm sure there are many more but those are the ones I've seen recently.