My tab knob broke so I made a new one. Fits on a 9.5mm knobbly bit on the faucet. Has 16 teeth.
Included are the Fusion360 source files to edit and make your own. It's mostly parametric, so just make an adjustment to the sketch and the rest of the feature should propagate.
There is a thicker version that feels better in the hand and would probably end up stronger. May be more suitable for PLA. I recommend using this one.
Also added a knob test file which is just a small section of the connecting part you can print to see if it fits your tap properly. Scale by a few percent to get it just right. You want it to be a very tight fit so that the teeth don't slip. You may want to heat up the knob with a lighter or something first and then heat press the plastic onto it.
For outdoor use, use a plastic like ASA which has better UV and temperature resistance.
I'm a perfectionist who likes making custom things, and building a reprap printer scratches those itches perfectly. There's nothing more satisfying than designing a part to fix a specific problem and pulling off the perfect print to do it.