Remember back in the 60s and 70s when you got a rifle from Sears or even Winchester, many of them came with a very simple sling strap? Those slings were just a long piece of 1" wide leather and has a loop on one end, close by a few sex screws, and they came back on the strap with a double loop slider to adjust for length and form the 2nd loop.

Does anyone still make those old style sling straps?

I always preferred the double loop 1907 style US Military slings for all my rifles, but on the old classics of European styling, the simple metal slider type slings are wonderful, and very easy to adjust for length.