Metex 9802A Frequency Adjustment Potentiometer

[Azimath]

Hello,
   I have a Metex MXG 9802A function generator and found that the frequency adjustment was not working at all. Upon disassembly I found that the frequency adjustment potentiometer has a bit of plastic connecting the shaft to the wiper which had come apart. My problem is that the potentiometer shaft is something I've never seen where the center shaft acts as a fine adjustment through some sort of ball bearing arrangement either as a planetary gear or to set the right amount of friction between shafts. The potentiometer is otherwise an ordinary looking 50kOhm one. The shaft was attached to the plastic by putting it through a hole then punching the end of the shaft so I cant install it onto a new potentiometer.
Is it possible and or worth it to get an exact or close replacement? I wasn't able to find one on Google since I dont know exactly what this is called. Should I just install another 50k pot? (I can live without the adjustment but would prefer to repair it with the right part if it isnt unreasonable to do so)

Thank you,
   -Azimath