Rain-X makes one.
If treating the glass isn't enough, you might try to find an oversize drinking straw (sometimes called a "wide" straw) as an easier to carry and use alternative to a snorkel. An ice cream shop might have just the thing for milkshakes and other thick drinks.
Here's another you can try, it really works. I use it on the inside surface of a motorcycle face shield in colder weather. Strange name, good product. ;)
Soap. Use a glycerin soap and rub it dry on the GG then buff it off. You can moisten it a little, but not wet - buff off when dry. It doesn't last forever of course, but it works and it's cheap.
Don't use it on your lenses of course.
Pentax used to make an anti-fog lens cleaner but I haven't seen it in a while. It also left a visible residue on the glass 9as it must to work), but it would clean off with regular lens cleaner or alcohol.
There was a product called fog off. It was an orange waxy stick that you rubbed on glass, then buffed. It worked really well, even filled in tiny scratches on my plastic eyeglass lenses. Alas, I haven't been able to find it again. The latest stuff I use for anti-fog is called Cat Crap. It's a paste and works similarily to the fog off product. It is available in safety supply stores.
Quite a few suggestions - some insane :-) but why not go to your nearest ski shop and get a little bottle of whatever fluid they sell to spray/wipe on the inside of ski goggles to prevent fogging. Saved me from impacting trees at Thredbo many a time!
have fun next season at Threadbo ... winter is starting here in Finland ... who knows we may get snow worth skiing on this year without heading 1000km north ;-)
where can i buy the best groundglas there is for my Crown Grapich 4x5" ?