Unable to install current version of El Capitan

I offered to help a friend upgrade her MBP to El Capitan from Yosemite. Unfortunately, the installer requires her to first install OS 10.11, the very first version of El Capitan. It’s no longer available online from Apple, and all the so-called “safe” sites where El Capitan OS 10.11 is allegedly stored are unreliable, slow, or both. Thus, there’s no way to upgrade to El Capitan. She’s stuck. Apple formerly kept earlier OS versions available just for this purpose. Its new policy of not doing so is essentially shooting itself in its foot.

Robert Jacobson about OS X El Capitan