I bought mine from klr650.com for $24.95 with a Hi / Lo switch included.
Now's heres the trick; you "Must" put Heat Shrink Tubing (you can buy from KLR650.com) over your Left handle bar to "Insulate" it from the Aluminum bar or else the bar will "suck" too much heat from the heater and burn it out.
- The right side is ok because of your plastic throttle sleeve is off the bar itself and is thus insulated.
-In addition the second problem is getting your Stock grip over the heat shrink and heater element on the left side. It can be done but the easier way is too buy to "Right" side grips (they are larger because of the throttle sleeve) and use it. sometimes you cannot buy just too right side grips and thus you have to buy two sets of grips and have two extra left grips leftover...
Hope this helps.
gman,