I've been waiting years for something like this to come to the states. Persu Mobility
http://persumobility.com/ (formerly Venture One) was supposed to have their "leaning trike" on sale by now. Who knows if their vehicle will ever come to fruition.
The BMW Simple Concept is the same kind of vehicle, but it's just a concept and is unlikely to ever be produced. (
http://www.bmwusa.com/Standard/Conte...e/Default.aspx)