I have been seeing a lot of questions like: "I want to install El Capitan, but I never got it from the App Store. How can I do this?"
The best option for this is "Get a friend with the installer." I have installers going back to Mavericks. Would it be useful and legal for me to create a Google Drive account where I could post these installers? The idea would be that I could create a canonical question/answer so that each time a question like this comes up, we can mark it as a duplicate of the question with a link to all of the installers.