I've made my own by simply getting a long leather dog leash at my local PETCO for about $10.95.

It comes with 1 spring loaded snap, so I bought another one for $0.95.

These leashes are about 60" long and are 3/4" wide, they are black, smoothed back and treated edge, they even come with beaded edges!

So I cut them to length (no adjustable buckle), folded the cut end, then drilled 4 x 1/32" holes, then stitched it all through the holes with shoe polyester thread (at my local shoe repair shop around the corner for $3.50 a roll of 100 yards.

So I now have a fantastic leather sporran strap for about $15, and I still have enough thread to make 2000 more.