There was a factory holster available, which adds up to $500 to the value of the gun, but I have no idea what it looked like.
I'm sure any custom holster or saddle shop, and most shoe shops would have been willing to make a holster for anything the customer wanted.
Getting such custom work done back in those days was easy, especially in shoe shops, of which there were plenty, and who were used to doing any leather work that came in the door.
Most of todays shoe shops are a pale imitation of the type of shops common up until the 1960's.