You can build your own w/ 3 SPST momentary switches and a TRS cable…
Switches are open-circuit and make a closed/short-circuit to sleeve/ground, etc when pushed.
Don’t use latching switches w H9, only momentary.

Button 1 shorts the tip to sleeve [T+S], button 2 shorts the ring to sleeve [R+S], and button 3 shorts both tip and ring simultaneously
More on this in the manual… easy to build and even easier to program…

MIDI is also another possibility. Hope this helps get the idea across…