I bought a Panasonic Tourist 3 with a Shimano 3CC three speed internal hub for my wife for on Valentine's Day. The stock sprocket is a 18t. I want to find a 19 or 20. On Shimano's web site they show Nexus three speeds with parts numbers for different sprockets. Does anybody know if these are compatable with the 3CC hub? If not, does anybody know a source for the correct sprockets?