Finding a 6 speed with an 11t is going to be difficult. There are 7 and 8 speed versions out there, but that would involve replacing most of the existing drive train. You best bet would be to swap out the chainring and ebait is a good source for rings and guards, as well as the usual suspects. Factor total cost for both scenarios and see which would be the best way to go. If you don't have much in the way of hills to deal with, the chainring would be the easiest solution.