Amazon.com: V-Color 32GB(2x16GB) 2666MHz ddr4 Compatible for iMac Retina 5K, 27-inch, 2019 and iMac Retina 5K, 27-inch, 2020 Non ecc SODIMM Mac Memory Ram Upgrade pc4-21300 CL19 260-pin 1.2V (TN416G26D819K-VC) : Everything
Timetec 32GB KIT(2x16GB) Compatible for Apple DDR4 2666MHz / 2667MHz for Mid 2020 iMac (20,1/20,2) / Mid 2019 iMac (19,1) 27-inch w/Retina 5K, Late 2018 Mac Mini (8,1) PC4-21333 /PC4-21300 MAC RAM at Amazon.com
64GB OWC Memory Upgrade Kit for 27-Inch Apple iMac 2017
64GB (4x16GB) DDR4-2666MHz PC4-21300 SO-DIMM Memory for Apple 27" iMac with Retina 5K Display Mid 2020 (iMac 20,1 iMac 20,2) by NEMIX RAM - Newegg.com
16Gb Ddr4-2666Mhz Pc4-21300 So-Dimm Memory For Apple 27" – TeciSoft
Hynix 16GB HMA82GS6DJR8N-VK 2666MHz DDR4 RAM is SODIMM PC4-21300 Mac Mini iMac Memory - Newegg.com
iMac 2019 - upgraded w 2 extra ram and the speed dropped to 2400 MHz? | MacRumors Forums
32GB PC4-21300 RAM for Apple iMac 2020 - 27 Inch Retina 5K MXWU2LL/A - MXWU2xx/A Memory Upgrade Module — A-Tech Memory