Amazon.com: OWC 32GB (2 x 16GB) PC19200 DDR4 2400MHz SO-DIMMs Memory Compatible with Mac Mini (Late 2018), 27" and 21.5" iMac (Mid 2017), and Compatible PCs (OWC2400DDR4S32P) : Everything Else
A-Tech 32GB (2x16GB) RAM for Apple iMac 2017 (27 inch Retina 5K & 21.5 inch Retina 4K) | DDR4 2400MHz SODIMM PC4-19200 2Rx8 1.2V 260-Pin SO-DIMM Memory Upgrade Kit at Amazon.com
Crucial Ballistix Sport LT 2400 MHz DDR4 Laptop iMac Memory Kit 8GB (4G x 2) | eBay
16GB PC4-19200 RAM for Apple iMac Mid 2017 - 27 Inch Retina 5K MNE92LL/A - MNE92xx/
Apple 32GB (2 x 16GB) 2400MHz DDR4 SO-DIMM PC4-19200 Memory Upgrade for Late 2015-2017 iMac 27 inch with Retina 5K Display at Amazon.com
64GB (4X 16GB) DDR4 2400MHz PC4-19200 SO-DIMM RAM Memory Upgrade for 2017 iMac 27 inch with 5K Retina Display (PARTS-QUICK) - Walmart.com
32GB Memory Kit for 27-Inch Apple iMac (2017)
Crucial 8GB DDR4 2400 MHz SO-DIMM Memory Module for Mac
Apple Memory Module 16GB DDR4 2400MHz SO-DIMM (2x8GB) - Apple
Apple Memory Module 32GB DDR4 2400MHz SO-DIMM (2x16GB) | Bridge Street Town Centre
Amazon.com: OWC 64GB (4 x 16GB) PC19200 DDR4 2400MHz SO-DIMMs Memory Compatible with 27" iMac (Mid 2017), and Compatible PCs (OWC2400DDR4S64S) : Everything Else
Crucial 8GB DDR4-2400 SODIMM Memory for Mac | CT8G4S24AM | Crucial.com
iMac 2019 - upgraded w 2 extra ram and the speed dropped to 2400 MHz? | MacRumors Forums
Crucial 16GB DDR4-2400 SODIMM Memory for Mac | CT16G4S24AM | Crucial.com