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.
Hey Jeremy, my name is Tom. I've been pouring over your old d95 curtis compressor rebuild thread. Fantastic work sir! I recently aquired a compressor that is the exact same model as yours and am currently in the tear down phase. My question for you- what type and where did you source the new piston rings? I have been searching the internet and can't find anything for this pump! Curtis toledo was no help at all.