OWC 64GB (4 x 16GB) PC21300 DDR4 2666MHz SO-DIMMs Memory Compatible with Mac Mini 2018, iMac 2019 and up, and Compatible PCs (OWC2666DDR4S64S) at Amazon.com
Crucial DDR4 Ram 8GB 16GB 32GB 64GB PC4 2133 2400 2666MHz ECC REG Server Memory support X99 motherboard RDIMM/LRDIMM _ - AliExpress Mobile
Crucial RAM 64GB Kit (2x32GB) DDR4 3200MHz CL22 (or 2933MHz or 2666MHz) Desktop Memory CT2K32G4DFD832A at Amazon.com
HPE 815101-B21 64GB 4DRX4 DDR4-2666MHZ LR Smart Memory
Micron 64GB (2 x 32GB) DDR4 2666MHz SODIMM Memory Upgrade Kit Compatible with 27 inch iMac (iMac19,1 iMac20,1 iMac20,2) - Walmart.com
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
Apple 64GB DDR4 R-DIMM ECC Memory Module Kit (2 x 32GB) MX1J2G/A