27" Late 2013 iMac Full NVMe SSD Upgrade - YouTube
Apple iMac 2013 (Late) 21.5-inch (iMac 14,3) SSD ,Ram & OSX Upgrades - ZD Laptop Service Centre
Amazon.com: PCIe NVMe Gen3x4 SSD 1TB 512GB 256GB 128GB 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
iMac 2013 (and later) with NVME SSD? | MacRumors Forums
Amazon.com: OWC 1TB Aura Pro X2 NVMe SSD Upgrade Kit Compatible with Select 27" and 21.5" iMac Models (Late 2013 - Current) : Electronics
Apple iMac 21.5-inch and 27-inch (Late 2013) reviews | Macworld
SSD Upgrades for Apple iMac 27-Inch Late 2013 - 2019
Configure your own 21.5-inch Apple iMac (2013) at OWC