8GB (4x2GB) DDR3-1333MHz PC3-10600 Non-ECC UDIMM 2Rx8 Desktop Memory Module by NEMIX RAM at Amazon.com
Hynix 4 GB UBDIMM 1333 MHz PC3-10600 DDR3 SDRAM Memory (HMT351U6BFR8C-H9) for sale online | eBay
A-Tech 8GB (2x4GB) RAM for Apple MacBook Pro (Early/Late 2011), iMac (Mid 2010, Mid 2011, Late 2011), Mac Mini (Mid 2011) | DDR3 1333MHz PC3-10600 204-Pin SODIMM Memory Upgrade Kit at Amazon.com
Apple Memory Module 8GB 1333MHz DDR3 (PC3-10600) - 2x4GB at Amazon.com