Bob has 'em (or I should say plans on getting them) - but they arent cheap at $9500.00. One attractive feature on the EM is the electronic clutch. I would think if you've built up years of reflexes to stop forward progress with your left finger it might be tough to get used to winding off the throttle (especially if you are hanging off the back of the bike at the top of a big step or something....)
Gas Gas has an electric too, via a partenership with ETA motors, http://www.eta-motors.com/verkauf-conversion-kit/
And, again, a conversion kit is 6195 euros - much more than a new gasser. The Gas Gas importer has a bike, but I have never talked to anyone who has tried it out. The gas gas spain website has the txt-e on thier website listed as "coming soon".
So, to summarize, until the prices drop to a level at or below that of a gas powered bike, and the performance of them is proven, they are going to be a tough sell.