Amazon.com: GODSHARK mSATA to A1398 A1425 (2012 & Early 2013) Adapter for MacBook Pro Retina SSD Replacement, Mini PCIe SATA SSD Converter Card : Electronics
How to Upgrade the PCIe SSD in a 13-inch MacBook Pro w/ Retina display (Late 2013 - Early 2015) - YouTube
MacBook Pro (Retina, 13-inch, Mid 2014) - Technical Specifications