This is a discussion on Shoulder rig for a Sig P238 (Or Colt Mustang I suppose) within the Defensive Carry Holsters & Carry Options forums, part of the Defensive Carry Discussions category; Andrews and Ritchie leather probably make the best shoulder rigs out there, but a rig like they make is usually meant for a larger gun ...
Andrews and Ritchie leather probably make the best shoulder rigs out there, but a rig like they make is usually meant for a larger gun so I doubt too many shoulder holsters of that style are made for the mustang or P238. You may want to look into KL Null holsters, they seem kind of strange at first but they are great for shoulder carry of small firearms because the rigs are light.
I use a Galco Miami Classic for my Glock 27. They aren't cheap but a good rig is worth the money and in the long run you'll be happier than with a cheap version.
I had the same problem finding one for my P238-HD. I ordered one from Ross leather, save your money it turned out to be garbage, the one they show online and the one that arrived looked nothing alike, cheep leather, the weapon didn't fit properly in the holster and the snap wouldn't stay closed. I tried the Barsony leather holster (also garbage), and the Bianchi X-15 holster which was very well made and comfortable, but the holster is way too large for a small weapon (comes all the way down to your waist). Finally I ordered one from JR Roscoe, its a custom fit holster, they get all your measurements and such when you order it; couldn't be happier with the way it fits, conceals, and the overall workmanship, the gun hangs exactly where it should without any adjustment straps, they look like something out of the old-West, but it does conceal the 238. I live in FL where its hotter than a camels anus, so I wear either a button-down or a guayabera shirt over a t-shirt without anyone noticing I'm armed.