Fingertip control for electronic knobs

I'm currently driving a new digital transmission electron microscope. The knobs which control the X and Y motion of the stage are so fluid and slick that they're hard to use, especially since I have to cover a large area (at least 1mm sq!) looking for virus particles.

Thus, this thing. It's sized to press-fit my stage control knobs, and has a fingertip indentation underneath (which becomes the top). Prints okay on a Makerbot in ABS even with the overhang. So now I can rest my fingertip on the indent of the knob and dial it to scan across large areas. Tested and it works.

Since it's unlikely that there are a lot of people out there needing a fix for the knobs on their H7600 TEM, and this is a stupid-easy CAD, I'm throwing this out into the 'verse as a concept: fix the knobs on the things you use every day.

Pic: note that the partial sphere used for the fingertip divot actually penetrates the bottom of the knob. Doesn't bother me, but you could make a smaller divot or make the k