OWC 32GB (4 x 8GB) PC12800 DDR3L 1600MHz SO-DIMMs Memory Compatible with 2011-2015 iMac Models (OWC1600DDR3S32S) at Amazon.com
NEMIX RAM 32GB (4x8GB Upgrade) DDR3-1333 PC3-10600 204-Pin SODIMM Memory for Apple MacBook Pro Early/Late 2011, iMac Mid 2010 27 inch 4-Core, iMac Mid 2011 21.5/27” , Mac Mini Mid 2011 at Amazon.com
Memory Upgrades for Apple iMac 2011 Up to 32GB
Apple iMac 27" Mid 2011 QHD i7-2600 32GB Ram 1TB HDD AMD HD 6970M HS OS DMG2 | eBay
Upgrading 27" iMac (2011) To 32GB Of RAM - YouTube
Imac 27 inch - 1tb ssd + 1tb sata, 32gb ram, apple keyboard and logitech mouse for Sale in Cupertino, CA - OfferUp
Amazon.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 : Electronics
Timetec 32GB KIT(4x8GB) Compatible for Apple DDR3L 1600MHz PC3L-12800 CL11 for iMac (Mid 2011, Late 2012, Late 2013, Late 2014 Retina 5K, Mid 2015 Retina 5K) SODIMM Memory Module MAC RAM Upgrade at Amazon.com
Adamanta 32GB (4x8GB) Apple Memory Upgrade DDR3/DDR3L 1600MHz PC3L-12800 SODIMM Compatible for Mid 2015 Retina 5k, Late 2014 Retina 5k, Late 2013, Late 2012, Mid 2011 iMac 2Rx8 CL11 1.35v RAM at Amazon.com
iMac RAM upgrade: Here's an affordable way to improve multitasking - CNET