Those little hand warmers...I think they're filled with some sort of iron and an oxydizer of some sort. An ample supply of those around the base of your gear should keep a little bubble of air around your camera that remains above the dew point.

Dew point is key. That's the temperature at which the air at it's current humidity will no longer be able to hold its water vapor, and the excess will be depoisted as dew. You only need a couple of degrees. Perhaps even a little tent or bivouac with a few hand warmers in it will give you the extra degree or two you need.