How about a new flyer, one sent only to the teachers, that says, "I will/will not participate in the PTO's efforts this year by circulating flyers to students in my class." Then beneath that, explain to the teachers that their responses will determine who will or will not continue to receive funds and other assistance from the PTO.
I suppose I'm kidding, but not by much.
We're lucky enough to have a wonderfully supportive principal who went at our teachers with both barrels when one made a snide remark to our PTO president as she was putting student flyers in mailboxes; the principal basically told the teachers that the school cannot ask the PTO to help them make ends meet in countless ways while simultaneously obstructing its efforts. Given what I've read elsewhere about your principal, you obviously can't count on her for backup, unfortunately.
Perhaps you could formulate some kind of communication to the teachers that would seriously outline what you do for them and what you expect in return--worded as a gentle reminder and request for, or even "thanks for," their cooperation? (Personally, I would write one the way I would LIKE to say it and then throw that away and do a real one!)