Howdy,
A local NAPA shop also services electric motors and other things. They were able to source the parts, but I don't know from who exactly. They sent the crank and pistons off to a vendor who cleaned up the crank (it was scored a bit), and provided new bearing shells and rings. They also re-bushed the con rod small ends on both rods. Getting accurate measurements of the ring lands and cylinder bores should let any good auto machine shop find a set of rings. I don't think they are anything special.