I recently purchased an Arai helmet and the thing is a fog machine. Pisses me off as it is dangerously bad. I don’t understand why Scorpion can make fog free helmets and others cannot in helmets that cost 3 to 4 times as much.
Anyway I recently made my first purchase of an anti-fogging product and I went for Clarity DeFog as reviewed in webbikeworld. They seemed to like it and so far I have been very happy with it. Might be worth a try if you are desperate. Not sure how it compares to the other products out there.