4GB -2x2GB Memory Ram Upgrade for 20" Apple iMac-7.1 2.4GHz Core2Duo Mid 2007 | eBay
A-Tech for Apple 6GB Kit (1x2GB + 1x4GB) DDR2 667MHz PC2-5300 200-pin SODIMM for MacBook (Late 2007, Early 2008, Early 2009), MacBook Pro (Mid 2007, Early 2008), iMac (Mid 2007) - Memory RAM Upgrade at Amazon.com
How to Install RAM in an iMac: 5 Steps (with Pictures) - wikiHow
The infamous 2007 iMac on Catalina | MacRumors Forums