Amazon.com: 2nd HDD SSD Hard Drive Caddy for Apple MacBook Pro Unibody Mid-2012 A1278 13-Inch Laptop MD101LL/A MD102LL/A MD101 MD102, SATA3 Second Solid State Drive Enclosure, CD DVD SuperDrive Optical Bay New :
Old MacBook Pro repair. Back when you could upgrade the SSD and Ram! : r/mac