Hi, I recently acquired an older albeit great 2012 iMac with an HHD. Being the newer, refined aluminum frame, I don't want to open it up to install a SSD. I have a Samsung 840Evo SSD that I had previously purchased for my PC that I now no longer have. Would like to house my SSD externally and connect via Thunderbolt to my iMac -- preferably to boot Yosemite from. Does anyone have suggestions for obtaining an enclosure in a rather Frugal means?