Heated Grips

I got the standard R3 kit fitted when I bought the bike, but the outer surfaces of the grips have now gone manky - presumably with the heat. I saw a classic last week with really nice heated grips which had the Triumph Logo moulded in. Anyone know if you can buy just the outer sleeve - or a more general question - is the heating element under the rubber or embedded in it. If it's underneath presumably any new rubber grips could be slid over?
Mike
 
****!!! Mine just failed.