Kingston Technology 4 GB Memory for Select Apple Imac's and Macbooks Single (Not a kit) 1066 MHz (PC3 8500) 204-Pin DDR3 SO-DIMM KTA- MB1066/4G at Amazon.com
Crucial 4GB DDR3/DDR3L 1066 MT/s (PC3-8500) SODIMM 204-Pin Memory For Mac - CT4G3S1067M at Amazon.com