How to Upgrade/Replace the PCIe SSD in a 21.5-inch iMac (Late 2013) iMac14,1 iMac14,3 - YouTube
SSD Upgrades for Apple iMac 27-Inch Late 2013 - 2019
Amazon.com: OWC 1TB Aura Pro X2 NVMe SSD Upgrade Kit Compatible with Select 27" and 21.5" iMac Models (Late 2013 - Current) : Electronics
Upgrade Kit For Apple Ssd 256gb Nvme Pcie 3.0 655-1993 Mz-kpw2560 For Macbook Pro Retina For Mac Pro For Imac Polaris - Pc Hardware Cables & Adapters - AliExpress