You could indeed use two MIDI faders - I’ve done so for creating a
Wavestation SR joystick in the past, and you simply need them to output controllers #16
The Yamaha TG or SY synths ought to do the job as well, and the Korg
However, but I wouldn’t recommend the old Korg keyboards, since
these often generate pitchbend in the left and right directions, modulation on the
‘up’, and breath control on the ‘down’, making it more difficult to translate to
the desired two controllers.