Timetec 16GB KIT(4x4GB) Compatible for Apple DDR3 1067MHz / 1066MHz PC3-8500 CL7 Dual Rank for iMac (Late 2009 21.5-inch / 27-inch) SODIMM Memory MAC RAM Upgrade for iMac 10,1 and iMac 11,1 at Amazon.com
Apple iMac 2009 A1312 MB952LL/A 27" C2D E7600 3.06GHz, 12GB RAM, 1TB HD Catalina 885909286300 | eBay
OWC 16GB (4 x 4GB) PC8500 DDR3 1066MHz SO-DIMMs Memory Compatible with iMac 21.5" and 27" (October/2009) at Amazon.com
A-Tech for Apple 2GB DDR3 1067MHz / 1066MHz PC3-8500 SODIMM iMac (Early/Mid/Late 2009, 20/24 inch, 21.5/27 inch), Mac Mini (Early/Late 2009 Mid 2010) Memory RAM Upgrade Module at Amazon.com
Review: Apple's 27" big screen iMac (late 2009) | AppleInsider
Apple iMac 27" Late 2009 i7-860 2.8GHz 16 GB RAM, 240GB SSD, Radeon HD 6970M 1GB | eBay
Apple iMac 3.0Ghz Core 2 Duo 21.5-Inch (Late-2009) *No HDD/RAM* – MSU Surplus Store