The mask will need to be painted white or off white like most of them came from the factory. Then weathered with soot and dirt a bit to get that worn wasteland look. Also there wash some kind of mesh like mosquito netting attached inside the mask around all the holes except the eyes.
As far as the neck brace, I think it is a posture collar as used by some BDSM folks. Also his body harness comes from the same type of outfits. As far as where to find the collar, I have no idea.
"Among other evils that being unarmed brings you it causes you to be despised" Nicolo Machiavelli