Tandy used to have leather, but haven't seen the name for quite awhile.
I get my supplies from Zack White. Find em on the net.
Your cost will depend on how much leather you buy and the thickness.
I think I bought a half a hide a few years back and am still working on that after a number of holsters, including a shoulder rig for a scoped RUGER Mark II Slab Side and a few that took a couple to get what I wanted.
Crusty Deary Ol'Coot