I am not sure I have the best answer, but I carry mine in an old Dillon spring clip IWB holster I bought for a PPK/S. It works perfectly and I have not seen one for sale since.
I bought Galco pocket holster and a Galco IWB holster for the mustang and found the IWB is too thin on the top for easy holstering. I am using the pocket holster now that it is getting warm for shorts carry.
Advice? Look at PPK/S holsters also. You want a good solid lip on the top of the holster to hold it open for holstering. Galco is good, Dillon was better. Galco pocket carry is good.
10mm and 357sig, the best things to come along since the 38 super!