I have a couple of really well-designed, well-made, OWB "pancake" holsters for my Colt's Model M. They were made by Ed Buffaloe.
Click on: 1903 & 1908 Colt Holsters
There's confusion about the name of this pistol. Its "given name" is the Colt's Pocket Hammerless.
The .32 ACP version is called the Model 1903. The .380 ACP version is also the Model 1903. In either case, you specify the caliber. Both guns are Colt's Model M.
(The Colt's Model 1908 is a different, tiny, .25 ACP pistol.)