broken volume knob on 2007 e70 x5

[Ron07x5]

My 2007 x5 does not have navigation. My radio volume knob is broken. The volume knob wiggles side to side like it's core shaft is broken. One still can press the knob in carefully to turn off and on the radio but one can't twist the knob to change the volume. So I must use the steering wheel volume control and I fear the knob may totally fail and then I will not be able to turn on or off the radio.

One apparently can not just buy the knob but must instead replace the full unit.
Cost of a new radio like $1600?

So can I salvage another a knob from a used navigation unit or must I find a radio only unit which seems harder to find.