The Model 39 was S&Ws first double action semi auto pistols and one of their neatest. I have a nickled one that I bought in the 60s and still love how it feels in hand. There are several different holster makers that offer excellent holsters for your pistol, you first have to decide how you want to carry it. I preferred IWB design for concealed carry but a tight, high riding OWB design works well under a sports coat or suit jacket. I suggest you visit online sites of various makers or better yet if you can find a dealer who stocks a lot of holsters. With a dealer you can actually try the holster so there's no guessing. Good luck with your Model 39, they are very good pistols.
Congratulations on a fine purchase. I used the Milt Sparks Summer Special when I carried a 39. I believe Galco produces something very similar now. The Bianchi #3 Pistol Pocket is another good IWB design.
For OWB a pancake design like that pioneered by Roy Baker and now copied by everyone is hard to beat.
If you carry concealed the hammer spur will chew up whatever garment covers it. We used the rubber caps from the hooks on the coat rack in the Investigations Division office to cover the spur and protect our jacket linings. If you don't have that option, your local hardware store sells a little rubber cap they call a thread protector. Find one (preferably in black) that fits snugly over the spur.
Thanks for the idea of covering the hammer spur! I didn't even think about that. I'll have to head to the hardware store to grab a thread protector tomorrow. The Milt Sparks summer special looks really nice. I might have to head to the gun shop to try some on and see what I feel is most comfortable to me. Thank you much for all your advice!