Sarah asked me to design KC-135 knobs for the sim she is building. This picture was supplied for reference.
Sarah also supplied the dimensions the part was to fit on making the design for the 'D' shaped to fit very simple. Less than 10 minutes later, two versions of the knob were designed. A raised line for ease of painting and a more traditional engraved line. Both accepting a D shaped shaft held in place with an M3x8mm Grub screw.
If you are interested in these knobs, you can find them here for download: