Amazon.com: OWC 2TB Aura Pro X2 NVMe SSD Upgrade Kit Compatible with Select 27" and 21.5" iMac Models (Late 2013 - Current) : Electronics
How to Upgrade/Replace the PCIe SSD in a 21.5-in iMac (2019)
SOLVED: Can I attach m.2 ssd heatsink to the 2019 iMac 27inch? - iMac Intel 27" Retina 5K Display 2019 - iFixit
Timetec 256GB MAC SSD NVMe PCIe Gen3x4 3D NAND TLC Internal SSD Compatible with Apple MacBook Air (2013-2015, 2017), MacBook Pro (2013-2015), iMac (2013-2019), Mac Pro (2013), Mac Mini (2014) - Walmart.com
Amazon.com: LEVEN 1TB Mac Upgrade NVMe SSD PCIe Gen3x4 Compatible with Apple MacBook Air (2013-2017) & Pro (2013-2015), Mac Mini (2013) & Pro (2014), iMac (2013-2019) : Electronics