Knobs for Siemens w295b

Hi All

I recently bought some Siemens w295b equalizer modules.  They are for the most part working, save some problems with the knobs.  On one, the low frequency knob is unresponsive.  Reptil (Jan) from gearslutz was kind to show me this: http://www.elma.com/Americas/English/Products/RotarySwitches_4/SelectorSwitches_30/290.aspx

I would love to know if anyone has had success replacing the frequency selector knob?  And if so, with what part?  I am looking at the schematic on Kubarth, but cannot ID those knobs.

Thanks a lot!

-David