From the first photo here 2399 triple splashback delay there clearly is more than a mm between the edges of the big knob and the board… I’m guessing he’s using this
https://www.rapidonline.com/sci-rn-114b-arrow-control-knob-37mm-32-0120
which is 37 mm diameter.
I have some MF-A05s coming but at 45 mm they’ll be too large for this. And for almost anything, but I can dream. MF-A04s [as linked above, “Boss style”] are 33 mm and should be okay.
The “small” knobs he uses I would guess are these
and the MF-A02 at almost exactly the same diameter would be a good match, but Tayda doesn’t have it and AliExpress stores mostly have only the 6mm shaft version. The MF-A01 linked above is okay but on the small side.