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

Update: after only a week, Plasti-Dip has proven to be even more bullshit than Sugru.
@jwz do you have a workshop that repairs/maintains sailing ships/yachts in your city? Try there. These people do not do online. From my experience only plain old rubber will do. Everything else is most probably useless.