Hohner Harmona electric harmonium

[sinewave]

Dear community,
I am not sure I am posting this in the right forum section, so I apologise if that's the case. Recently, I have purchased an electric harmonium and I am trying to bring it back to the full working order. So far, the sound is nice. But, the potentiometer (see attachment) which controls the speed of motor has oxidised and it doesn't work through it's entire range. It can't slow down the motor to the minimum because the wires in the lower potentiometer range are disintegrated. I have searched for the similar type of part and all I could find is very expensive wire potentiometer (300 €). Is there any cheaper solution? Thank you for your suggestions!
Sinewave

[SubBase]

Could you adapt something like this? https://ipv6.fasttech.com/product/72...gulator-pwm-ac

[tpappano]

In the picture it looks like the motor is a 'universal' ac/dc type. You could also try a simple incandescent lamp dimmer, cheap and easily available.

[sinewave]

Thank you for your ideas! I will research both of them and hopefully find a good solution! Cheers!