How about using a MIDI keyboard…?
Centred around a D key … …
lower F# could do Channel Down (Velocity might even adjust the speed of the repeated presses 
)
lower G# could do Channel Up
lower A# could do channel Select
lower A could do Back Down
lower B could do Back Up
lower C could do Back Select ( This would sit under the left hand thumb)
Higher E could do Select Select (This would sit under the right hand thumb)
Higher F could do Select Down …
Higher G could do Select Up
Higher F# could do LS Select
Higher G# could do LS Down
Higher A# could do LS Up…
