Ramjet 4GB DDR3-1333 PC3-10600 DDR3 1333Mhz SO-DIMM for Apple MacBook Pro (1x 4GB) at Amazon.com
Other World Computing - DDR3 - kit - 8 GB: 2 x 4 GB - SO-DIMM 204-pin - 1333 MHz / PC3-10600 - CL9 - 1.5 V - unbuffered - non-ECC - for Apple iMac; Mac mini (Mid 2011); MacBook Pro (Early 2011, Late 2011) - Walmart.com