The IRD thumbies look very similar to the microshift ones - the lever especially looks exactly the same. Do you know if the IRD levers have a friction option?
And can anyone point me in the direction of the XC Pro diagram?
there might be more info out there. it looks like the only thing needed for 9 speed conversion is to make another cam plate. I can't be sure without seeing one myself, but maybe the existing cam plate could just be turned over and drilled on the other side? Some careful calculation and drilling would be needed, but I reckon it should be possible to do.