In ANH they had Racal head sets under their helmets.
Same ones worn by the ground crew and on the Falcon.
There was a pic floating around where you can see most of it under the helmet.
If you can find a real Racal headset that answers that. In ESB and RotJ its the same Racal headset minus the rubber tip on the microphone.
The earcups, like Ed suggested, are hearing protectors from a safety supply store. Remove the cushion, paint them dark grey and put the cushion back on. Apply inside the helmet with velcro.