Let Friction Ring.

Dear Lazyweb, I have this pulley wheel, 50mm inside diameter, 4mm groove. I need a rubber traction ring to go inside it. I cannot find anyone who will sell this to me. The ring must be flat or concave, not round like a typical...
https://jwz.org/b/yk33

@jwz Maybe you've already looked here, but if McMaster Carr doesn't have what you want, it probably doesn't exist
https://www.mcmaster.com/products/pulleys/

Can you replace the rope with a rubber belt? https://www.mcmaster.com/products/pulleys/round-belts-1~/

Pulleys | McMaster-Carr

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@grwster No, replacing the rope is not an option. The problem with McMaster is that I demonstrably don't know what the thing I am looking for is called, so can't search for it.