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) on Vimeo
240GB OWC 6G SSD and HDD Kit for 27-inch iMac all 2012 - Mid 2019
How to Upgrade the Main Drive in a 27-inch iMac (Late 2012 – 2019) - YouTube
iMac (27-inch, Late 2012) - Technical Specifications