REPORT: The Aerostitch grip wraps listed above work very, very well. Installed them in under an hour this past weekend (and I'm not a fast mechanic). Used 'em last night when the temperature was high 30s low 40s with a pair of unlined gloves and my hands were perfectly warm -- hot, even!
At least for now, I'm judging these things a fantastic buy for $50.
The only thing one needs to be careful of is that they're wired straight to the battery, so if you forget to turm them off, you'll have warm grips but a cold battery.
--Jaeger