udenjoe
2
Get something that is shaped different would help too!
I’m not sure this is the correct size (6mm)
http://www.gravitech.us/blrukn146mmd.html
Or if shape doesn’t matter you could get the knob upgrade from Elektron.
http://www.elektron.se/content/mdmono-knob-upgrade-kit
Here’s another:
http://www.mcmelectronics.com/product/28-11826&scode=GS401&CAWELAID=1292681692
You just need to know the dimensions of the length and width of the shafts. Search “d-shaft knob”