The Gerbing homepage http://www.gerbing.com/pages/dealers/thedealers/AZscottsdale.html
says the nearest authorized is in Scottsdale
www.bmwofscottsdale.com
but BMW of SD doesn't say anything about it.
There appear to be 7 Widder retailers in AZ http://www.widder.com/html/Dealers/index.htm
But if you have a choice, go Gerbing. Got my wife a pair of Gerbing gloves to wear in the car, Her hands turn pasty white in the cold, and it's great for her to be able to plug the gloves in her car.
Happy Hunting