I could be wrong but my instincts tell me you would have to fabricate or use some sort of rearset system w/ a linkage arm like the sportbikes and mini gp bikes in order to make this happen. Probably difficult with as close as the peg is to the shift lever but, not impossible.
Reason is you basically want the lever to work the opposite way but, the counter shaft as to turn the exact same way to shift gears. Therefore you have to create the same leverage motion via the opposite direction. There as to be something to reverse the motion.