i currently have two Sony MZ-R50 minidisc recorders. these recorders are from 1997, and don't have features like MDLP or NetMD. they are still both extremely solid, however.
one unit currently works flawlessly, and the other is broken. it fails to read the disc. the one that works is in amazing condition, with only a few scratches.
i tried to modify the sony lip-8 battery it came with to install a new sanyo ur14500 cell, but failed. i found a Sanyo UR14500 cell, which was compatible with the original 14650 cell, but a bit shorter. unfortunately, i did not order it with tabs welded to it, so i tried to use springs from a battery compartment, but accidentally melted the casing with my soldering iron. i will try again with another battery whenever i get one.