Gene, have you looked at this sort of thing? VHT Vinyl dye

I've used the satin black on things like sun visors etc and as it is an actual dye (not a paint - ie it is very thin going on) it seems to work quite well. Is the HZ cap a type of rubber like the earlier models? I do know that they do not wear so well in high useage areas like steering wheel grips but the horn pad might be OK as it isn't being constantly touched or abraded.