Here is my collection of knobs designed for mechanical keyboards and standard EC-11 rotary encoders. More will be added as I design more. However, CAD files are included for you to mod on your own.

Stovetop Style Parametric Knob:

This file is mostly parametric in Fusion360 by editing the user parameters, and the included .stls are for a 25mm knob.
 

Simple Knob- 3 Sizes available- This is a basic knob designed for mechanical keyboards, and fits standard EC-11 D shafts found on most keyboards.

• 25mm
• 19mm (this is the most common and takes the place of a keycap)
• 14mm

I've included .step or .f3d files for easy modding to size in CAD or going wild with it. I've also included a handy 3dp insert if you resin cast or mill knobs. This file works best resin printed, but it prints fine with an FDM printer with .4mm nozzle. They are designed to be mostly a press fit, but may need some super glue to keep it in place.