8GB kit (2x4GB) DDR3 1066 SODIMM for Apple iMac (2009), MacBook Pro (2 – Aplus Technology
How to Upgrade iMac RAM (21.5" and 27" Aluminum): EveryMac.com
A-Tech for Apple 2GB DDR3 1067MHz / 1066MHz PC3-8500 SODIMM Memory RAM Module for MacBook, MacBook Pro, iMac, Mac Mini - (Late 2008, Early 2009, Mid 2009, Late 2009, Mid 2010) Models at Amazon.com
Apple A1225 24-inch iMac Core 2 Duo 2.4 GHz 2 GB RAM 320 GB HDD Early 2009 | RecycledGoods.com
iMac 24-inch Early 2009 – Full Tech Specs, Release Date, and Price