You could try partnering with some companies that make applications geared toward your users and set up an affiliate system. My company makes a basketball app

You could try partnering with some companies that make applications geared toward your users and set up an affiliate system. My company makes a basketball app http://www.slyceapps.com/shottracker http://www.slyceapps.com/shottracker and our customer base seems to overlap with yours. Find others like myself and reach out to them.