You'd probably benefit from looking in the "Greaser Fashion" section of this site since that's the kind of look that both Brando and Dean had popularized in their films like "The Wild One" and "Rebel without a Cause"
Brando's clothing in the movie, "The Wild One" consisted of the following:
1. Black leather "greaser" style jacket from the manufacturer Schott (Jacket is called: "One Star Perfecto Leather Motorcycle Jacket ") http://www.schottnyc.com/motorcycle-leathers/one-star-perfecto-leather-motorcycle.htm
2. Engineer Boots (Here's a replica: http://www.askmen.com/fashion/apparel/frye-brando-engineer-boots.html)
3. T-Shirt (or rather an undershirt)
4. A pair of beat up Levi's jeans