8GB [2x4GB] DDR3-1333 RAM Memory Upgrade Kit for The Apple iMac 12,2 (27-inch, 2.7GHz, MC813LL/A) Quad-Core Intel Core i5 (Genuine A-Tech Brand) at Amazon.com
Differences Between Mid-2011 and Late 2012 Aluminum iMac: EveryMac.com
Timetec 32GB KIT(4x8GB) Compatible for Apple DDR3 1333MHz PC3-10600 CL9 for iMac (Mid 2010 27 inch, Mid 2011 21.5/27 inch) SODIMM Memory Module MAC RAM Upgrade for iMac 11,3 / iMac 12,1 / iMac 12, 2 - Blumaple LLP
OWC 16GB (2x8GB) ram Upgrade PC3-12800 DDR3L 1600MHz sodimm 204 Pin CL11 Memory Upgrade Kit Compatible with Late iMac, Mac Mini, and MacBook Pro Computer at Amazon.com
Best Buy: Apple® iMac® 21.5" 8GB Memory 1TB Hard Drive A1311
iMac i7 Memory Model 11.3 (i5 and i7) 12.1 & 12.2 | Ramjet.com