Check out the Headsets Inc. headset- I've got both that and a David Clark, and although the passive noise reduction is better in the DC (important for open-cockpit stuff) I think the ANR feature is just as good (if not better) in the Headsets' version, and the last I checked it's substantially cheaper.
They also make a do-it-yourself ANR kit for David Clark's, but you've gotta be better with a soldering iron than I am to make it work.