In my opinion, the HH mic is only for clarity and stick definition, and almost any pencil style condenser will work since it only gets about 50% or less of the level of any other mic in the kit setup. Oktava MC012 or MXL 603s are great. Also shure SM94 and SM81. Usually the overheads pick up enough, but having one about 4-6 inches above the hi-hat, pointed at where the stick hits works if mixed in just enough.
In other words, a mic that responds to fast transients and has good high end definition. Any mic that works well as an overhead is fine for high hat. Personally, I believe that mic'ing high hat is unecessary, as a rule. If you want to bring it out in the mix, just reposition the oveheads to emphasize the high hat.