Handcar belt slipping

[EEB]

I have an old handcar (track workers).  The electric motor shaft is connected to a drive pully bya small elastic belt which has stretched to the point it will no longer grip the pulley/shaft. Any suggestions as to how to get a replacement belt or modify the drive mechanism?

[Loco Bill Canelos]

I don't have one but several folks have told me they used an O-ring which may be found at plumbing stores or hardware stores to replace it. they took the old one with and bought O-rings in several sizes the same size and several slightly smaller sizes til they found the one that worked.

Hopefully there is a better answer from another poster!