Two things:
Mechanics Wear Gloves:
All Gloves : Mechanix Wear
I like the camo ones, but there's plenty of options out there. If none of these are warm enough,l check out hunting gloves at Cabelas, Bass Pro Shops, Gander Mountain, etc. The whole point is to have enough warmth to keep your fingers ready for the quick reaction needed.
The other thing is hand warmers. There are many options that you can pick up almost anywhere. I have two things I use. One are the packets you can buy at most sporting goods stores and Wal-Mart that are good for 6-8 hours of warmth. The other are battery operated versions that keep hands warm too.
Besides this there are a wide variety of things including battery warmed clothing itself. Go into a sporting good store and check out the options. There's lots and one will work well for you!