If you've got a Tandy store near you, they usually have classes on the basics. I've made my own holsters and tack for our horses since the 70's. It's not brain surgery and you can make any type that suits you.
I make a paper pattern to fit the gun + 3/4" all around. Then cut the leather using heavy shears or a utility knife. I use heavy, 8-9 oz. tooling leather.
I glue the belt loop down with Barge Cement...from Tandy's...and stitch it, using the old two needle technique. I space the holes out using a spur type of device, then drill the holes for the needles with a 1/16" drill or a cut off nail.
Once the flap is stitched, I cut a piece of leather to form a welt, along the lower barrel up to the trigger guard. This is glued in place, then marked, drilled and stitched as well.
For finishing, I bevel all cut edges, then burnish with a sanding drum on an electric drill. An older drum is best. The edges are wet before burnishing allowing the leather to round over and get a hardened edge.
I wet the entire holster, the use my fingers to fit it to the gun. Wrap the gun in a baggie first, form the leather to it, then remove the gun and let the leather dry...24 hours.
I use Snowproof boot waterproofing on all my work, but if you want a darker color, Tandy's sells stain and the sealer necessary to keep it from bleeding into your clothes.
Here are a cpl of my efforts, and some of the tools necessary to make them. Get with the people at Tandy's...they'll be glad to help.
Best Regards, Rodfac
The tools...
Two useful books on lacing and stitching.
Close up of the grooving tool etc used to sink stitching below the surrounding leather to keep wear to a minimum. The fork tool is for beveling the edges. The spur lays out the hole spacing for stitching.
The welts on a Tom Threepersons holster.
Some finished work. The belt is my version of the Duke's rig...rough-out money-gunbelt.