These are similar to many of the others out there. I just decided to model them after the feed wheels and handles on lathes and milling machines.
Like the others 2 - 8 mm x 3 mm magnets super glued on the back.
Thanks to Petclaud for this great idea.
I will warn you the knob is a little tough to print. I may need to revisit this one someday.
Just for fun, I put one of the feed wheel 2's on the X axis stepper. It really reminds me of a milling machine in operation.