In addition to your in-person research, library databases and retailer corporate websites will likely aid you the most in completing your project. A quick summary of the best databases to use is below.
Public companies' websites often provide their annual reports, financial filings, and other information to the public through sections of their corporate websites. Search for the company's home page, (try a company's name or well-known brand and "corporate website") and look for a tab or link that mentions investors or financials. Note that if your retailer has a parent company you may find this information in their report.