You are probably both correct in your belt size statements. V-belt manufacturers measure their v-belts on what they call the "pitch" length. This measurement is about 3/4 of the way up the belt. This is always shorter than the outside dimension.
Mituboshi (note mitsubOshi not mitsubIshi) has a factory office in Ohio but they will not sell the belt because it is propriatary to Honda. Honda sells it but wants $$$$$
Try one of the others as referenced in the previous postings.