SOLVED: Use of Samsung 950 PRO M.2 256 GB SSD - iMac Intel 27" EMC 2639 - iFixit
Amazon.com: INDMEM 512GB NVMe PCIe SSD 3D TLC NAND Flash Hard Drive Disk 512G Only for Late 2013 - Mid 2015 MacBook Pro, Mid 2013-2017 MacBook Air, Late 2013-2017 iMac, Late 2013
Sintech m.2 PCIe NVMe 2013 2015 Apple MacBook Pro Air Mini iMac 固态硬盘适配器| eBay