If you look at the underside of most MC's there is a number stamped into the bottom. It represents the bore size. At least on Yamaha's for sure. So if you're looking for a MC of a certain size you could go do a dealer and look at the underside or ask an ebay seller to look for the stamp before you bid.
Another option is to go with 1" bar riser reducer sleeves. or cut your bars down and have the ends replaced with 7/8 bar. For example. I have 1.5" bars on my raider but they reduce to 1" at the ends to accomidate for the controls and MC.