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 Memory Module 32GB DDR4 2400MHz SO-DIMM (2x16GB) - Apple
16GB Kit DDR4 Memory (2x8GB) Apple iMac 27-Inch 2400 MHZ 2017 model A1419 | eBay
iMac 2019 - upgraded w 2 extra ram and the speed dropped to 2400 MHz? | MacRumors Forums
OWC 64GB DDR4 2400 MHz SO-DIMM Memory Upgrade Kit
parts-quick 8GB (2 X 4GB) Kit Memory Module for Apple iMac 27" 2017 5K Retina Display DDR4 2400MHz SO-DIMM RAM at Amazon.com
Crucial 8GB DDR4 2400 MHz SO-DIMM Memory Module for Mac
Timetec 16GB Compatible for Apple 2017 iMac (27-inch w/Retina 5K, 21.5-inch w/Retina
32GB Memory Kit for 27-Inch Apple iMac (2017)
Amazon.com: OWC 8GB (2 x 4GB) PC19200 DDR4 2400MHz SO-DIMMs Memory Compatible with Mac Mini (Late 2018), 27" and 21.5" iMac (Mid 2017), and Compatible PCs (OWC2400DDR4S08P) : Everything Else
Apple Memory Module 16GB DDR4 2400MHz SO-DIMM (2x8GB) - Apple
Crucial 16GB Kit (2 x 8GB) DDR4-2400 SODIMM Memory for Mac | CT2K8G4S24AM | Crucial.com