64GB RAM upgrade kit for 21.5-inch iMAC now offered by OWC - 9to5Mac
Timetec 64GB KIT(2x32GB) Compatible for Apple DDR4 2666MHz for Mid 2020 iMac (20,1 / 20,2) / Mid 2019 iMac (19,1) 27-inch w/Retina 5K Display, Late 2018 Mac Mini (8,1) PC4-21333 / PC4-21300 MAC RAM at Amazon.com
A-Tech 64GB (4x16GB) RAM for Apple iMac 2017 27 inch Retina 5K | DDR4 2400MHz SODIMM PC4-19200 2Rx8 1.2V 260-Pin SO-DIMM Memory Upgrade Kit at Amazon.com
Apple iMac Pro 27-inch 3.0GHz Intel 10-Core / 64GB RAM / 2TB SSD / Vega 64 16GB | eBay
Timetec 64GB KIT(2x32GB) Compatible for Apple DDR4 2666MHz for Mid 2020 iMac (20,1 / 20,2) / Mid 2019 iMac (19,1) 27-inch w/Retina 5K Display, Late 2018 Mac Mini (8,1) PC4-21333 / PC4-21300 MAC RAM at Amazon.com
64GB Memory RAM Kit for Apple iMac 27 DDR4 2400MHz, PC4 19200: Amazon.de: Computer & Accessories
Timetec 64GB KIT (4x16GB) Compatible for Apple 2017 iMac (27-inch w/Re
64GB (2x32GB) DDR4 ECC Memory Kit - Apple
A-Tech 128GB (2 x 64GB) RAM Kit for Apple iMac Pro (2017) - DDR4 2666MHz PC4-21300 ECC LRDIMM 288-pin Memory Upgrade Kit at Amazon.com
64GB Kit 4X 16GB Apple iMac Late 2015 Late 2012 A1419 MD095LL/A Memory Ram | eBay
OWC Confirms New Low-End 27-inch iMac Can Be Fitted With 64GB RAM - MacRumors