MCE Technologies 2TB Internal SSD Flash Upgrade for 13" and 15" MacBook Pro Retina (Mid 2012 - Early 2013) - Includes Installation Kit!
A-Tech 8GB RAM for Apple MacBook Pro (Mid 2012), iMac (Late 2012, Early/Late 2013, Late 2014, Mid 2015), Mac Mini (Late 2012) | DDR3 1600MHz SODIMM PC3-12800 204-Pin SO-DIMM Memory Upgrade at Amazon.com
How to Upgrade MacBook Pro RAM (2009, 2010, 2011, 2012): EveryMac.com
Apple MacBook Pro with Retina display review (mid 2012) | Engadget