Check out Strapworks dot com
I gave up on buying stuff other than Stainless snake chains & now make what I need. Check out Strapworks.com (in USA). They have nylon/polyester etc (no leather) strapping a variety of widths & tons of colors. Also metal (including brass) & plastic hardware (slides, rings, Dees, clips. From the one detailed photo above it looks like you can thread a strap through the slots. I have a Mamiya 220 with their snap-on peg thing & shelled out for the OpTech thing with the specific tabs. Next time I'll just make something.
If you save your own old hardware, other than the "look" the nylon works just fine.