If you don't mind a rivet showing, I don't see that you'd have to sew at all. I would take one long piece of leather that is already dyed, punch holes where you want the beads to stop on each end, and bend the ends of the leather over to the back to make the loops. Rivet the leather to itself and to the string. You could make a channel by carving an indent along the middle of the leather before dyeing. I've never made these but I imagine that might work. If you have trouble getting the beads to stay in the center, maybe punch a few holes to have the bead string go through to the back and then come right out the front again.