I believe the latest release available for El Cap was 7.9.7 (current as of posting is 7.10.7). You could try emailing ian@mactracker.ca and see if he can send you a copy of the earlier release.
This version could run on your macOS El Capitan release. OR at the very least have it update within the app to the latest know release for El Capitan
Last note is to enter the Mac App Store on El Capitan and find Mactracker there. If it's in your previous purchases you will hopefully get suggested the lasted version available for you via Mac App Store.
edited because I realized that El Capitan is macOS 10.11 and that particular version isn't on macintoshgarden.