Welcome..
Get your sound people to buy you a TD-20, there’s separate outs a plenty on that.
It is tricky when stereo out is all you have. You could hard pan some signals to one side, and some to the other, say kick and snare to the left, toms, and cymbals to the right.
Have a chat with the noise boys, see what they actually want.
I can’t think of any MIDI out device that might fix the problem, especially control of the individual triggers.
The only fix I can suggest is you trigger via MIDI another drum source, like a sampler, drum module, or drum machine that has separate audio outs.
You might be able to utilise some of the TD-9’s sounds using the hard pan left, and right suggestion, and
the additional source for the rest.
