Amazon.com: iFixit Battery Compatible with MacBook Pro 15" Unibody (Early 2011-Mid 2012) - Repair Kit : Electronics
Amazon.com: 2nd 2.5'' SATA HDD SSD Hard Drive Disk DVD CD ROM Optical SuperDrive Caddy Tray Adapter for Apple Unibody MacBook/MacBook Pro 13 15 17 Early mid Late 2008 2009 2010 2011 2012.etc : Electronics
How to Increase the Performance of an Old MacBook Pro [Tutorial]