3/4" thick UHMWPE
I used (2) pieces of UHMWPE. I had the material left over from a table saw fixture I made. Other materials such as nylon might work as well. Bolt them together and drill a 7/8" hole for the pedal shaft and one 1-1/8 hole for the handle post. I made it so the parts would clamp to the post, but free spin on the pedal shaft.
This is the only non steampunk material I used. I'll pretend it is whale bone, elephant tusk or some other politically correct Victorian material.
Update: I bought the UHMWPE on sale at a woodworking show. You can also buy it a McMaster Carr. The size used here (4" x 3/4") is about $11 per linear foot. You only need about 4" of it. It is nice stuff to have around for projects. It is very tough and nearly frictionless against metal. It can be easily cut, drilled with woodworking tools.