Apple 21.5" Pre-Owned iMac Desktop Intel Core i5 2.7GHz 8GB Memory 1TB HDD (2012) Silver MD093LL/A - Best Buy
Apple iMac 21.5" - Core i7 3.1GHz (Late 2012) 16GB RAM 1TB Fusion - Very Good | eBay
Memory Upgrades for iMac 21.5-Inch 2012 - Late 2013
Memory Upgrades for iMac 21.5-Inch 2012 - Late 2013
Install memory in an iMac - Apple Support
Timetec 16GB KIT(4x4GB) Compatible for Apple DDR3 1067MHz / 1066MHz PC3-8500 CL7 Dual Rank for iMac (Late 2009 21.5-inch / 27-inch) SODIMM Memory MAC RAM Upgrade for iMac 10,1 and iMac 11,1 at Amazon.com
What Does It Take To Upgrade a 2012 iMac 21.5"?
CMS 16GB (2X8GB) DDR3 10600 1333MHZ Non ECC SODIMM Memory Ram Upgrade Compatible with Apple® iMac 21.5-Inch 2.7Ghz Intel Core I5 (Mc812Ll/A) - A13 at Amazon.com