OFFTEK 8GB Replacement Memory RAM Upgrade for Apple iMac 2.7GHz Intel Quad-Core i5 - (21.5-inch) (Late 2013) (DDR3-12800) Desktop Memory at Amazon.com
Memory RAM Upgrade for Apple iMac 27-inch Late 2013 4GB/8GB DDR3 SODIMM | eBay
iMac with Retina 5K Display 2014/2015 Memory Upgrades
Memory upgrade: Apple iMac 2012/2013/2014 (Howto)
8GB -2x4GB Memory Ram Upgrade for 27" Apple iMac-14.2 Core i7 3.5GHz Late 2013 | eBay
Memory Upgrades for iMac 27-Inch (2012 - Mid 2015)
Adamanta 16GB (2x8GB) Apple Memory Upgrade DDR3L 1600MHz SODIMM Compatible for iMac (Mid 2011, Late 2012, Early/Late 2013, Late 2014, Mid 2015) 2Rx8 CL11 1.35v RAM at Amazon.com
NEMIX RAM 16GB Kit (2x8GB Upgrade) DDR3-1600 SODIMM PC3-12800 for Apple MacBook Pro Mid 2012 / iMac Late 2012 / iMac 2013, Late 2014, Mid 2015, Mac Mini Late 2012 at Amazon.com