I'm kind of curious why an "investor" would be so interested in a Rum largely used for mixing that was sub $20 when it went extinct in the states. But maybe you could try contacting the Mt. Gay distillery itself and inquire about possible sources directly from them.
If that doesn't pan out, see if your boss will settle for the
Mt. Gay Black Barrel Rum that averages in the mid $20's. It's vastly superior to the discontinued Sugar Cane variety IMHO. Anyway, good luck with your search.