Amazon.com: OWC 2TB Aura Pro X2 NVMe SSD Upgrade Kit Compatible with Select 27" and 21.5" iMac Models (Late 2013 - Current) : Electronics
2013 iMac teardowns reveal SSD slots, soldered-in CPU in the 21.5” model | Ars Technica
SOLVED: Can I create a fusion on late 2013 iMac 27? - iMac Intel 27" EMC 2639 - iFixit
DIY SSD upgrade kit for late 2013-2019 iMac|iMac late 2013-2019 SSD with upgrade kit|Flexx Memory|Free UK Delivery
DIY 2013 iMac SSD Upgrade! - YouTube
Amazon.com: USB C 3.2 Enclosure for 12+16 PIN MacBook SSDs, PCle SSDs Enclosure Supports for 2013-2017 MacBook Air, 2013-2015 MacBook Pro Retina, 2013-2014 iMac, 2013 Mac Pro, 2014 Mac Mini : Electronics
Timetec 512GB 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