Last year I fitted heated grips to my Fz600 but i found the feel difference betwean my other bike so strange that i had to fit a pair to the thou as well, At high speed on very cold days its strange having hot palms with cold knuckles, I might even consider the lever covers mentioned (fitted as standard to some Suzukis)
Heated grips or gloves are good but my heated under jacket is well worth the £40 I paid, makes cold days a pleasure.
Just got to get grips with the misting up helmet issue