maxupgrades.com: Single SSD Drives kit for iMac 27 inch 2012 Models with SATA Blade SSD Module / Heatsink/ Power Cable and DATA Cables for [SSD + HDD] with iMac Adhesive LCD Tape
How to Install/Upgrade the SSD Card Slot of a 27-inch iMac (Late 2012) iMac13,1 - YouTube