I ride a lot and have never seen any gadgets for fixing this. It depends on the snow as well, since the bigger wetter stuff (so cal / washington mountains) tends to be much more of a problem than the bone dry stuff (co / slc mountains).
Worse is that in conditions with lots of snow coming down you may want to wear goretex shell mitts, and regardless you'll have snow all over your hands since.... well... it's snowing.
I wipe my goggles off when I start going down a run with the sleeves of my jacket, and then I stop as often as I need to and rewipe, or do it during a non-technical stuff where I can move my upper body about.
If it's really dumping clumpy snow, it's going to get on your goggles and it's going to limit your visibility, there's not really anyway around that. But hey, it's powder. Keep the nose up, weight the back, and shred.
If you start losing visibility to the point that you're unable to see contours and terrain angles, it might be time to hit the lodge and grab a beer.