There is a slight amount of difference between the 3 types of spark advancers found in the 750 engines. The earliest ones are often marked "AD125" and have the shorter idle advance (by about 2 degrees) and advance the fastest (softest springs). The later ones are marked with the tiny Hitachi stamp or the TEC stamp: they have 2 degrees more idle advance, but the same full advance. The ones for the 750F2/3 engines have the same advance rate (in the springs) as the Hitachi version, and they are often stamped with "410" on them somewhere.
But, any one of those, or any one from a CB500/550, would work fine if you just need the cam to be locked in place and let the electronics do the advancing. You can also buy a brand new one, albeit with bizarre springs, from 4into1.com.