Couldn't find a replacement, but decided to restore it only for nostalgia reasons (it was an unobtainable item while I was a kid).
The potentiometer is indeed the stereo volume/balance/tone/on/off from a Romanian auto radio-cassette player designed during the communist era, about 30-40 years ago.
It took me acouple of hours to dismantle it, find a way to fix it then put the thing back. Even so, the time spent fixing it was less than the time wasted online searching for a (compatible) replacement. The potentiometer defect was that it was freely turning (it was supposed to have a limited turn angle) and the on/off was not switching at all. This is a pic with 3 out of 5 sections dismantled. The bronze lever on the axle was supposed to rotate various sections.
The bronze flattened part was suppose to come in touch with a small cap (made probably from ABS) that was turning the volume and on/off assemble. The middle of the cap was sanded with time by the bronze lever, so it was not possible tu turn the cap any more, that's why the free turning knob:
A small metal insert cut from a Champagne metal bottle cap was melt into the ABS sanded cap in order to restore the full functionality:
And the whole assembled thing former unobtainium now looks like this:
Decided to use it as a dedicated audiobook player in the kitchen: