I have a 2008 iMac - How do I get Yosemite or El Capitan. Sierra will not install.

I have a 2008 iMac - How do I get Yosemite or El Capitan. Sierra will not install (i do not want to hack it either).

I never 'got' Yosemite or El Capitan when they were available on the Mac App Store.

The only way I have found is to get it from the Apple Developer site but I am not a developer. How do I get Apple to flip the Mac App Store switch so it shows up on my list?