OS X Yosemite Download

Hello Community!

I've recently moved back home from college and there is an unused iMac (mid 2006) that was running Snow Leopard. I've caught it up to OS X Lion but my quest to bring this iMac to today's software (erhm, well, Yosemite since that's the latest OS that is compatible with the 2006 iMac). I've tried burning several online dmg files of Yosemite to a bootable USB (as I did with Lion, successfully). However, I can't seem to find a download link that works, and most end up telling me to open the app store (where Yosemite no longer exists). I called Apple support and they referred me here. Would anyone have a download link, or a dmg file for Yosemite that works? Or perhaps an alternate course of action is to be taken?

TL;DR: I need an OS X Yosemite dmg file or a download link for a bootable USB.

Thanks for your time, practitioners of Macintosh.