A friend with an AI here in Wyoming has found the following invaluable:
1) A goretex dry suit with integrated socks. We have suits made by Kokatat. While pricey, they may save your life. An added bonus is that they add substantial flotation. Wearing heavy fleece pants and top inside adds a lot of warmth.
2) Extra warm neoprene gloves.
3) A neoprene face mask used by skiers.
4) Chemical warmers. Go to www.warmers.com
for more info. You can't wear them next to skin because of the heat they generate. You can put them into the goretex socks of your drysuit. A muff of some kind lets you occasionally slide a hand in to warm up a bit. Warmers.com has a "Cozy Muff" designed for this (which unfortunately isn't waterproof; good luck rigging something up).
Two AI's on order for springtime '08 delivery,