OWC 64GB (2 x 32GB) PC21300 DDR4 2666MHz SO-DIMMs Memory Compatible with Mac Mini 2018, iMac 2019 and up, Dell, HP, Lenovo, ASUS and Compatible PCs (OWC2666DDR4S64P) at Amazon.com
Micron 64GB (2 x 32GB) DDR4 2666MHz SODIMM Memory Upgrade Kit Compatible with 27 inch iMac (iMac19,1 iMac20,1 iMac20,2) - Walmart.com
CMS 64GB (4X16GB) DDR4 21300 2666MHZ Non ECC DIMM Memory Ram Upgrade Compatible with HP/Compaq® Omen Obelisk Desktop 875-1xxx Series, Pavilion 690-0013d Gaming Desktop PC - D56 - Walmart.com
OLOy DDR4 RAM 64GB (2x32GB) 2666 MHz CL19 1.2V 260-Pin Laptop Gaming SODIMM Upgrade for 2019/2020 iMac 27-inch with Retina 5K Display Late 2018 Mac Mini (MD4S322619MZDC) at Amazon.com