OWC 64GB (4 x 16GB) PC12800 DDR3 1600MHz SO-DIMMs Memory Compatible with 2015 (Late) iMac 27" w/Retina 5K Models and Compatible PCs (OWC1600DDR3S64S) at Amazon.com
64GB (2x32GB) DDR3-1600MHz PC3-12800 ECC LRDIMM 4Rx4 1.5V Load Reduced Server Memory by NEMIX RAM at Amazon.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