I have Symtec heaters on my VFR and KLR. They are inexpensive and easy to install under just about any standard grip. I have factory blasters on my Wing.
My Order of Preference for heat is:
1. Warmer gloves for short trips. I also use them with grip heaters.
2. Grip Heaters
3. Grip Heaters and Electric liners for frigid conditions
I also keep wool liners in reserve.