Are you going to cut belt slots for attachment? If so, it's hard to tell from the pic but it looks like the slots will be rather small, maybe not. My recommendations are to wet mold the holster, cut the belt slots, sew as closely to the gun as possible and hopefully, round off the square corners at the bottom of the holster a little bit.
For sewing, I use a drill press with a 1/16" bit to drill the holes. Tandy sells waxed linen thread (or waxed nylon) and stitching needles (10 pack). The 25 yard spool of thread will do at least half a dozen holsters.
After sewing, sand the edges, dye the holster if you want, slick the edges and finish with a top-coat.
Nick