Upgrading an older iMac's PCIe SSD: Third-party solutions that save you beaucoup bucks | Macworld
Amazon.com: INDMEM PCIe NVMe Gen3x4 SSD 1TB 3D TLC NAND Flash Hard Drive SSD Replacement for MacBook Air 2013-2017, MacBook Pro Retina 2013-2015, iMac 2013-2017, Mac Pro 2013, Mac Mini 2014 (1TB) : Electronics
M.2 NVMe SSD Convert Adapter Card for MacBook Air Pro Retina (Year 2013-2017), NVME/AHCI SSD Upgraded Kit for A1465 A1466 A1398 A1502 - Newegg.com
Amazon.com: OWC 2TB Aura Pro X2 NVMe SSD Upgrade Kit Compatible with Select 27" and 21.5" iMac Models (Late 2013 - Current) : Electronics