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
Upgrading a 27-inch iMac 5K to 14 terabytes - Replacing the Fusion Drive with both a SSD and an harddisk
iMac Hard Disk Removal | iMac SSD Upgrade | Thermal Sensor Link Posted under Description - YouTube