Amazon.com: Timetec 16GB KIT(2x8GB) Compatible for Apple DDR3 1333MHz PC3-10600 CL9 for Mac Book Pro (Early/Late 2011 13/15/17 inch), iMac(Mid 2010, Mid/Late 2011 21.5/27 inch), Mac Mini(Mid 2011) MAC RAM Upgrade :
A-Tech 32GB (4x8GB) RAM for Apple iMac (Mid 2010 27 inch 4-Core, Mid 2011 21.5/27 inch) | DDR3 1333MHz PC3-10600 204-Pin SODIMM Memory Upgrade Kit at Amazon.com
How I kept my iMac running for a decade | Cult of Mac
How to upgrade RAM / Memory on a 2010 iMac Core i3 i5 i7 (21.5in & 27in) - YouTube
How to Upgrade iMac RAM (21.5" and 27" Aluminum): EveryMac.com
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