Don't see why you couldn.t DIY some.Possibly using the $1.99 Radio shack electret microphone elements (though unidirectional is probably better),battery box to bias the mics and a simple gain stage.I would probably add a VOX (voice operated relay) to the circuit so it would only be "on" when talking ,or at least a noise gate (Analog Devices combo mic preamp/noise gate chip SSMXXXX)
Attaching them ? Some small diameter aluminum or brass tubing (brake line material ?) , large enough in diameter for the mic cable to snake down it.I would cover this with heat shring tubing to keep mic noise down , plus add a small windscreen-also from the shack.Sticking it to the headphone-
option # 1 : since the entire assembly would be very lightweight you could epoxy a good size alligator clip to the shaft , clipping the whole thing to a convenient spot on the cans
option #2 :More permanant- drill a small hole somewhere on the earpiece and then seal the area with silicon caulk,maybe there IS a use for the Grado Button
Use your imagination man , should not be too hard to do this
Rick Out