The Correct Plural form of a Feminine Noun Meaning "One Who Gives Blowjobs"

Via e-mail I've been told that my use of the word fellatrixes (referring to female campaign lobbyists) might be incorrect. The e-mailer was right in pointing out that the strictly Latinate plural ending would have resulted in "fellatrices."

I confess I'm not sure. A google search indicates that my version is the more popular one; however, that doesn't mean that it's grammatically correct.

The evidence in my favor is that modern English tends to add English noun endings to even purely Latin words: stadiums, not stadia; museums not musea. Interestingly, the Latin plural "agenda" has become a singular in English (does anyone out there say "agendum"?) while the bastardized plural "agendas" is commonplace. On the other hand, we still preserve the datum/data distinction (even if datum is out of favor), and similarly declined words (e.g. matrix/matrices) go against the trend in preserving the Latin ending. [Could that be because those words tend to be technical?--ed.]

In order to avoid this dilemma, I plan to revert to using the good ol' Saxon "cocksucker."