Our old fashioned One Man Band is just like the one from the old circus and carnival days. It features the musician (Larry pictured above) playing bass drum, hi-hat cymbals, banjo, harmonica, kazoo, slide whistle, siren, bell, ratchet and tambourine all at once. The mobile set up, pictured at the top, features the musician with the bass drum strapped to his back, making it possible to have a marching or strolling one man band. The bottom picture is of the stationary set up, as featured on Michael Moore's TV NATION. The costume and repertoire are generally "Americana" style, though that can be altered to fit your requirements.
It's important to note the difference between this act and the more modern one man band that is sometimes requested. The phrase "one man band", in the modern sense, is used to describe a guitar or keyboard player with a synthesized drum machine and a full sound system. The modern version is available also, but only in the stationary (not strolling) configuration.