Just found this option:
http://www.wirelessground.com/sc5310.html
It seems to be precisely what I was looking for initially. I would think I could find a decent noise-cancelling microphone with a 2.5mm connector, plug in the 3.5mm cassette adapter, and pass through power as well using this one adapter.
Does anybody know of a good noise-cancelling microphone that I could use with this setup? The Monster one is giving fairly bad echo is the stereo is on too loud.