Does such a law specify it HAS to be on the outside of the vehicle? A mirror on the back of each wheel fairing might actually work pretty well, and have no aerodynamic impact.I knew that vehicle manufacturers have standards set by the federal government governing mirror size, placement, and reflectivity of mirrors however I did not know what standards were set by states for mirrors. It turns out that most states have very basic mirror laws only requiring at least one mirror on motorcycles and two on cars, including one left side mirror, and just about every state has a statement like this one: Every motor vehicle, operated singly or when towing another vehicle, shall be equipped with a mirror so located as to reflect to the driver a view of the highway for a distance of at least 200 feet to the rear of such motor vehicle.
What I would do when replacing full sized side mirrors with cameras is include a small mirror in a position close to the body that also still gives rear visibility of at least 200 feet. This way you get most of the aerodynamic benefits while also meeting the letter of the law.