A thought occurred to me regarding the PianoDisc player. I have never
looked at the insides of one, but most of the 3.5" disk drives were,
for the most part, interchangeable, using the standard floppy disk
interface cable and a 5-volt power source.
I would rather suspect that a 1.4 M drive would drop right in the disk
player with no changes. A 1.4 M drive will read 720 K disks OK; so
reading older disks would not be a problem, and you could then use the
1.4 M disks which are still available. Newegg shows 1.4 M disk drives
for around $15.00; so cost is not a problem, and almost any computer
geek could make the swap successfully.