I have been told that the telephone mics that have a suction cup built into them work well. I have never tried this myself, but I assume that the cup would be attached to one of the headset cans.
Would love to know how you make out since I'd like to try the same at some point.
Another thought would be to have the speaker in the aircraft going and hope the camcorder picks it up - probably try that one if all else fails!
