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
SSD Upgrade Kits for 27-Inch iMac (2012 - Early 2013)
Apple iMac 128GB PCIe Internal SSD Hard Drive Storage (Samsung MZ-KPW1280/0A7) | eBay
How-To: Now's the right time to swap your old iMac's hard drive for a fast new SSD - 9to5Mac
iMac (20-Inch, Early 2009) SSD Upgrade - YouTube
How to Upgrade iMac Pro SSD (Replace Storage): EveryMac.com
How can i choose to boot from the second SSD harddisk for a mid 2011 iMac? - Ask Different