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
The Sonnet M.2 4x4 PCIe Card adds insanely-fast SSD speeds to Mac Pro
Upgrading an older iMac's PCIe SSD: Third-party solutions that save you beaucoup bucks | Macworld
Amazon.com: FLEANE FM13A 1TB PCIE 3.0x4 NVME SSD with DIY Tools for MacBook Air A1465 A1466 (Mid2013-Mid2017), MacBook Pro Retina A1398 A1502 (Late 2013-Mid 2015), iMac A1419 A1418 (Late 2013-Mid 2017) (1TB) :
DATARAM 1TB M.2 M-Key PCIe NVMe SSD for 2013-16 MacBook, Mac Pro, Air, Mini, iMac - Walmart.com
Genuine Apple 4TB (2x2TB) PCIe SSD for: 2017 iMac Pro A1862; 2019 Mac Pro A1991 | eBay
128GB FUSION DRIVE PCIe SSD Apple iMac 21.5" A1418,27" A1419 Late 2013,2014,2015 | eBay
How to use an NVMe drive to upgrade your Mac's SSD | AppleInsider
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