Went into dealers today. Apparently there are three different kinds of heated grips (according to which model of Mutley you have). They didn't have mine in stock. Both my grips have gone so it's £195 + VAT + labour (about 1 1/2 hours for the single spark model where the tank needs to come off). All told just over £300 I said I'd leave until when I needed them i.e. winter!
I have a Mulstistrada 1200S with grip failure. If you are interested, I put a detailed video together on how to go about doing this work. For US $40 you can repair these on your own. I hope this helps you. John