16GB DDR4 2400MHz PC4-19200 SO-DIMM RAM Memory Upgrade for 2017 iMac 27 inch with 5K Retina Display (PARTS-QUICK) - Walmart.com
Crucial 8GB DDR4-2400 SODIMM Memory for Mac | CT8G4S24AM | Crucial.com
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
Amazon.com: A-Tech 32GB Kit (2x16GB) RAM for Apple iMac & Mac Mini (2018, 2019 & 2020) | DDR4 2666 MHz SODIMM PC4-21300 / PC4-21333 260-Pin SO-DIMM Memory Upgrade : Electronics
The Mizzou Store - iMac 27" 5K 6C 8GB 256GB
Apple iMac review: A 27-inch work-from-home beast with a killer webcam - CNET
64GB Memory Upgrade for 2019-2020 Apple iMac (27-inch)