Well boys, a knob's a knob by any other description ! So to be serious for a moment or two, I have my doubts that either of the two would be available separately. It's the whole cable or nothing, and the price will really make one blush and fumble for the razorblade. I've forgotten how much I was quoted a few years ago, but it was not cheap.
Incidentally, talking of that cable, I have only ever come across one unit that was actually user friendly - you know, easy to pull and push. The graduations of positions can be a little haphazard to determine, and I would rather leave the cable loose under the bonnet in order to effect adjustments and ease of checking the position of the disc on top of the distribution valve. Phew - that WAS long winded. Regards Styria