I'm not sure that the general expectation that "Morris" will be an all male activity holds true to any great extent these days, I think that most people understand that it is an activity participated in by both sexes, either individually or in mixed sides,...indeed I think many people believe that this has always been the case !!
There is no "scale Fee" for such things, and as Will says, performers will negotiate a fee they are happy with depending on what they have to offer to a potential booker, sex does not, or should not come into it,.. If the fee does not meet your expectations you don't do the job, .....same as in any trade or profession.!!!