The best resource available at USC for supplier information is Bloomberg. (See instructions to the right on.) FITA is another great source.
Bloomberg's Supply Chain module can be accessed by typing SPLC <GO> if you already have a company selected. If not you will first need to select a company by typing and then SPLC.
Supply Chain data includes customer, supplier, and competitive relationship to track a company's performance against peers. It can be viewed in chart or table form. See the Bloomberg Guide for more information on using the terminal.