A Hair slicker might prevent some friction over this area, along with headgear that provides maximum coverage. If you can't find a headgear that seems appropriate I would contact the companies directly and explain the situation. They might have products for him that they don't list in the regular catalogs.
I think anything in the medical realm that you would find as far as protective wear would be a solid hard plastic type material that would not be appropriate for wrestling.
It is vital that he certainly protects this area.