I was looking for El Capitan for weeks and today I finally managed to get it. The Appstore no longer has OS X El Capitan available to download. To solve this issue follow this link:.
The Appstore only has updates but not the original OS. So If you did not download El Capitan before it was removed from the App Store then you will not be able to get it from the Appstore anymore. You can now only download it via alternative sources, Just make sure they are trusted sources though. Hence I recommended the link above. Hope this helps you also.
Download OS X El Capitan 10.11.6 Combo Update. Download OS X El Capitan 10.11.5 Combo Update. Download OS X El Capitan 10.11.1 Update.