Unfortunately doesn’t look like they sell the disc holder separately
Hmm that abit strange as this sort of quick change et up commonly comes with several. But as pointed, you can make your the grooves are nothing fancy and how they lock in is normally just a couple of O-rings.The pad I have i have is a standard roloc pad, but the shaft is not standard. I’d like a second shaft so I can quickly change between 2” and 3”. To do that now I have to unscrew the pad and screw a new one on. The shaft is quick disconnect from the handle. No tools needed.