128GB FUSION DRIVE PCIe SSD Apple iMac 21.5" A1418,27" A1419 Late 2013,2014,2015 | eBay
256GB PCIe Blade SSD Kit - Apple iMac 21.5" A1418 Late 2013,Mid 2014,2015 4K | eBay
Flexx LX300 512GB NVME SSD Kit for MacBook Pro, Air and iMac from late 2013 on | eBay
Amazon.com: Cloudeck NVMe SSD 512GB PCIe Gen3x4 Internal Solid State Drive with 3D NAND for MacBook Air (Mid 2013-2017), MacBook Pro(Retina, Late 2013- Mid 2015), Mac Pro(2013) & Mini (2014), iMac(2013-2017) : Electronics
Original 128GB PCI-e SSD Replacement for MacBook Pro Late 2013 - Mid 2014, MacBook Air Mid 2013 - Early 2014, iMac Late 2013 - Mid 2015, Mac Mini Late 2014 (Bulk, No Retail Packaging) : Electronics
Hard Lesson Learned With Late-2013 Apple Products Containing Lesser Performing 128GB SSDs | The SSD Review
How to Speed up your iMac with a NVMe 960EVO M.2 SSD - YouTube
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
SSD 1TB PCIe NVMe Gen3x4 3D TLC NAND Flash Hard Drive Disk 1T Replacement for MacBook Pro Retina Late 2013Mid 2015 MacBook Air Mid 20132017 iMac Late 20132017 Mac Pro 2013 Mac Mini 2014 - Newegg.com
SOLVED: Are these the right SSD PCIe blades for iMac Late 2013? - iMac Intel 21.5" EMC 2638 - iFixit
Sintech M.2 nVME SSD Adapter Card Upgrade Kits,Compatible for MacBook Air( 2013-2017 Year) and MacBook PRO(Late 2013-2015 Year,iMac : Electronics
2013 iMac teardowns reveal SSD slots, soldered-in CPU in the 21.5” model | Ars Technica