Amazon.com: New 16GB 4x4GB Apple iMac (21.5 and 27-inch, Late 2009) : Electronics
Memory Upgrades for Apple iMac 2008 - Up to 6GB
How To - RAM Upgrade iMac (Late 2007, Early 2008, Early 2009) GERMAN - YouTube
Apple iMac Late 2009 All in One Pc i7 16gb Ram 2TB HHD 2.8gz Selling as Is | eBay
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
Used Apple iMac 21.5-inch 500GB Hard Drive 4GB RAM I3 Proessor (Mid 2010) - ZD Laptop Service Centre