I love Work Louder's Creator Micro keypad, but I found that the rotary knob was a bit slippery and difficult to turn with one finger. 

This grip levels off the top and provides a grippy side surface that makes the knob easier to use with one finger.

This should work on any of the Creator series keyboards (Micro, r4, XL), though I haven't tested this on two immediately adjacent to one another. There may not be enough room for this grip to work on two that are side by side, but it'll work on any stand-alone knob. 

Print with TPU and enable the fuzzy skin setting in your slicer for best results.