Most cameras have the threaded hole on the bottom for the tripod mount you could just thread a bolt through the hard hat and tighten a nut on and screw the camera on ?
You wouldn't need a "mount" then. I'm gonna try it ?
Edit; Just bought one on Fleabay for 11.00 new.
http://cgi.ebay.com/NEW-Industrial-P...d=p3286.c0.m14