I got a complaint that the stock metal valve handle was too hard to turn because of the small ridges, so I made this one with a bit more leverage (much longer ridges) and only three bumps (instead of the usual six small bumps). It seems to do the trick and is much easier to handle.

Print with infill of at least 70% for strength.
I printed this one at 0.1mm layer height using PLA.
The handle fits on shafts with a square head.
The taps with a protruding screw (like shown in the photo) may require some handle-screw-hole reaming.
The taps with the extra screw may require some handle-square-hole reaming.