If you don't want something like the Oxford Hot grips and need heating from a specific type of grip then you need aftermarket kits that allow you to fit heating elements under you any grip you choose.
The two popular choices seem to be.
Symtec
http://www.windingroads.co.uk/shop/p...d0611ea3290aad
Aerostich
http://www.aerostich.com/review/product/list/id/278/
I have a spare set of the aerostitch if you are interested, a long story about postal delays and my impatience with freezing weather.