The Mission Statement for your company will usually be found in the COMPANY ANNUAL REPORT. Look for words like MISSION STATEMENT or LETTER TO SHAREHOLDERS.
What is the annual report?
The annual report to shareholders is the principal document used by most public companies to disclose corporate information to their shareholders. It is usually a state-of-the-company report, including an opening letter from the Chief Executive Officer, financial data, results of continuing operations, market segment information, new product plans, subsidiary activities, and research and development activities on future programs.
There are several websites that provide free access to annual reports. It is also often possible to find reports on a company's website, usually in the investor relations section.