
A Spanish company called Noomad is producing a kit that converts your two wheel machine into a three wheeler. The kit adds 18 or 20 inch wheels, dual disc brakes, and a parallelogram hub attachment that allows the wheels to lean into a turn. The kit bolts up to forks that have V-Brake or cantilever bosses.
The rig is about the width of typical flat handlebars. Might be a way to carry extra gear for those long unsupported rides.
The company sells complete bikes as well as kits, including a tandem that has simple suspension built into the fork.
http://www.noomadbike.com/en/