+1 for make your own. Mine is nylon webbing, velcro and a single metal D-ring. Goes through the sling slot and thumbhole and I clip an MS2 sling on it.
I also have a Cazador rear stock strap by Sling Guru but I've never tried it since it's designed to work with the Sling Guru Tactical Rifle Sling, which I do not have.
