I usually go to a supplier in Tucson....Rocking J Leather.
Tandy is a good place to start, they should have one semi close to you.
If you want to buy online from Tandy...get a 7-8oz shoulder, which should run about $40.00. You can get 3 holsters from it.
It is thicker, and leather shears are a MUST. Exacto knives just won't...wait for it....wait for it....cut it. Fine auto body sand paper from your local auto parts store is good for smoothing the edges. Wood sandpaper will come apart on you.
Like I said this is all advice from a hobbyist. Professionas will tell you I am wrong, and that I don't know what I am talking about. I just know what I use.