I tend to just use pirate bay and look for stuff that is verified in some way with good comments. Will likely need a mirror to get to it. Maybe rarbg.
I've recently done what you're looking to do for my girlfriends macbook that I think had CS5 which stopped working properly due to MacOS updates and I ended up jimming a CC version I think.
I'll be honest though, it was a pain in the arse to crack. Had to go to the mac command line and do some stuff, not really having a clue what I was doing. Eventually worked, but wouldn't remember how to repeat it.