CMS 8GB (2X4GB) DDR3 8500 1066MHZ Non ECC SODIMM Memory Ram Upgrade Compatible with Apple® iMac Core 2 Duo 3.06 21.5-Inch (Late 2009) - A35 at Amazon.com
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
Apple iMac 21.5" AIO High Sierra 3.06GHz Intel Core2 Duo 8GB Ram 500GB Late 2009 | eBay
iMac 21.5” Late 2009 Catalina 8GB RAM 256GB SSD- BEST OFFER for Sale in Katy, TX - OfferUp
Apple iMac A1311 21.5" Desktop - MB950LL/A (October, 2009) for sale online | eBay