The 3" 24's are great revolvers. You may want to keep an eye out for the S&W holster that was available and made specifically for the Lew Horton Model 24 3" back in 1984. You see them on the used market from time to time.
Second that on Mernickle. Purchased one of their rigs with ammo belt slides. Use the holster for all my 3in N frames. He made a custom holster for my special order SAA Sheriff's model. Frank Jr.
I use this J. W. O'Rourke pancake rig for my 3" 610-2. It works just as well for my 3" 25-14. I'm very happy with it. J.W. was great to deal with and it took less than a month to get.
Paul: I make holsters for the N-frames, including your 624 3-inch. Several styles available. Prices start at $39. Production time usually about 2 weeks. My e-mail address is in profile if you would like to see photos of my work.