"Someone told me that it was possible to buy heat packs to put into cycling gloves. The only ones I could find were 3x5"", which turned out to be too big to put into my lobster claw gloves or five-fingered gloves. (Also, the packs rest exactly where your palm presses against the handle bar.) Is there a place that sells smaller heat packs?"
Heat Packs for Lobster Claw Gloves
Polypropylene Liner Gloves inside my lobster claw gloves allow me to ride comfortably in cold weather down to about 25 degrees F. The main reason they work is that they keep the sweat off of your hands and build a small air pocket between your hands and the lobster claw gloves.
I don't suggest chemical heat packs because when sweat hits them they turn hard like rocks. In addition, for them to work well in really cold weather you'll have to position them at the tips of your fingers.
Here is a link to the performance website. Other companies may offer a similar type of glove - that wicks away moisture.
http://www.performancebike.com/shop/profile.cfm?SKU=14171&subcategory_ID...
I bought a pair at Dave's Army Navy on 6th Ave. 5 bucks.
I use thin glove liners I got from Sports Authority that have built-in pockets for warmers. The liners have metallic threads that supposedly distribute the heat. I use toe warmers in those pockets. The adhesive keeps them in place and they are thinner and less noticable than hand warmers. They're usually good for 4-6 hrs.
A friend lent me hers the other day running at Van Cortlandt Park. They were definitely small and fit comfortably in the palm of my hand, with my fingers curled about them somewhat (I was wearing mittens). She said you can get them at Paragon. They warmed my hands up nicely, after that if there is a sweat problem (as someone mentioned above) you could just slip them in a pocket or something. But, finally, who knows how they would work grasping handle bars? You'd just have to try. I think it would be doable.
I place them on top of my hands between my liner and glove. I have never experienced the moisture issue. I highly recommend them for people who have problems with the cold. You can buy them for $0.99 at Modells, or try your local hardware store. The cheapest option is bulk (10 pack) through Modells.com.