Abominable Labs is currently running a Kickstarter campaign to fund the F-BOM, a goggle that always eliminates fog.
The technology works like the defroster in the rear window of your car. A thin-film transparent heater, powered by a small lithium-ion battery, sits between the two-part goggle lens and keeps the temperature just higher than dew point, thereby wiping out any fog build up.
If you back their campaign, the goggles are yours for 195 clams. Get on it.