Google?
Spit and soap are your cheapest options. Most companies that sell goggles sell anti fox with them.
Also a fast search for "antifog" (first page):
http://www.airsoftcanada.com/showthr...hlight=antifog (in the FAQ...)
http://www.airsoftcanada.com/showthr...hlight=antifog
http://www.airsoftcanada.com/showthr...hlight=antifog
http://www.airsoftcanada.com/showthr...hlight=antifog (in the reviews section)
There is also ESS, Revision, Cat Crap, any ski company makes them.
Just have to actually go out and look. Try what works for you.
Personally the fog tech does nothing for me. Where as the revision stuff works great for my ESS goggles.