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
Install memory in an iMac - Apple Support
Memory RAM 1x 2GB Apple iMac Early 2009 DDR3 1066MHz SO-DIMM | E-OWC8566DDR3S2GB | APPLE \ MEMORY FOR APPLE \ OWC \ APPLE IMAC \ iMac Early 2009 \ iMac 24'' (Early
Apple iMac 24" Early 2009 Core 2 Duo; 4GB RAM; 640GB HDD | eBay