Gary, just do a google search for leaning sidecars, or to narrow it down look for Flexit sidecars and Equalean sidecars. The Equalean was designed and produced by Vetter, but was famous for cruiser fairings and still has helmets made under his name. He produced about 250 of them until the motorcycle bust of the early 80s. Flexit looks like a better one to me, but I don't know as much about it, but there's a lot of stuff out there on it. Plans and manuals are available.
Bare