Hello, my name is Tom Uffner, and I am an expert Webmaster and SysAdmin. I can help you with this project.
Assuming that you run your own site, or have sufficient access to your server to set cookies, get your access and error logs, and run programs or scripts, I can: 1) tell you the next URL any visitor goes to after leaving your site, 2) what other sites any returning visitor went to immediately after leaving your site.
You may also be able to have 3rd party advertisers tell you when and where they spotted one of your tracking cookies, but that would by a paid 3rd party service that I can not provide or control other than programming your site to set the appropriate cookies to be used by any such subscription services.