umm. the lenses are plastic so maybe you could use like meguirs plastx or some other similar product. Its for cars but it will accomplish the same thing. I haven't ever done it so i can't give input towards if it works or not. I dont know how this affects the antifog or the gas layer between the lenses. Just a suggestion.
I have always just bought a new lense. I wear electric eg2's and the lenses have never really been that expensive.