8GB -2x4GB Memory Ram Upgrade for 27" Apple iMac 11.3 Core i7 2.93GHz Mid 2010 | eBay
hardware - Can I add different size RAMs to iMac 5K? - Ask Different
Timetec Hynix IC 16GB KIT(2x8GB) Compatible for Apple DDR3 PC3-8500 1067MHz/1066MHz Upgrade for MacBook 13'' Mid 2010, MacBook Pro 13'' Mid 2010, iMac 27''Late 2009, Mac Mini Mid 2010(16GB KIT(2x8GB)) - Walmart.com
Installing additional SSD in Mid-2010 27" iMac
Install memory in an iMac - Apple Support
iMac RAM upgrade: Here's an affordable way to improve multitasking - CNET
Timetec Hynix IC 8GB Compatible for Apple DDR3 PC3-8500 1067MHz /1066MHz SODIMM Memory Upgrade for MacBook 13'' Mid 2010, MacBook Pro 13'' Mid 2010, iMac 27''Late 2009, Mac Mini Mid 2010 (8GB) - Newegg.com