Awesome! Always wanted to do something like this to use with just one finger like the jog wheel on the mackie MCU. Wonder if I can get this more locally in the US?
I’ve just bought “VA20 NITRILE Rubber V-Ring For Shafts 19-21mm” from a shop called Simply Bearings on E-bay UK, only cost £3.18 incl. postage, it stretches onto the controller knob and provides a lot more grip than the bare metal. I found that a number of retailers on the 'net do stock it also. I’ve no idea what it’s actually for, but it suits my purpose.
I have just found this post and ordered the Rubber V-Ring (I couldn’t find a UK stockist for the ALPS ring unfortunately…) will let you know how it goes!