A minus 20 degree bag eh? for less than $350? I think that means that top notch down bags like Western Mountaineering are out of the picture. Why not look at a quality synthetic bag? There's a weight penalty of course when you get away from down but there is less concern about getting you bag wet. I think Wiggy's bags are considered very good synthetic bags for extreme cold. Their Ultima Thule is a -20 degree bag and I notice they are currently selling it for $275.

Sounds like an interesting job! Why won't someone hire me to go backpacking?