Here's an update. I'm the OP and have tried some of the suggestions here. There really isn't a thin battery heated glove I could find that allows the use of fingers. The wires make the glove thicker and manufacturers add a thin layer of insulation that makes it too thick.
I did find some success in something mentioned here that I forgot. I put on a pair of thin rubber gloves like the surgical gloves so common today and then put my thin leather gloves over them. Rubber isn't supposed to insulate but my hands felt and stayed warmer for maybe an hour in 28 degree weather. Normally, I could only go maybe 15 minutes. That did work for me and no loss of dexterity. After a while let your hands warm up, change the rubber gloves and start over but for a lesser time.
Also, I've read that putting a small hand warmer on the inside of your wrist warms the blood and makes your hands feel warmer. I'd like to try it but the dry-packet hand warmers aren't hot enough and I can't find a quality metal hand warmer that's small. That's where I'm at.
Thanks for the great ideas.