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
16GB DDR4 2400MHz PC4-19200 SO-DIMM RAM Memory Upgrade for 2017 iMac 27 inch with 5K Retina Display (PARTS-QUICK) - Walmart.com
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
Upgrade your iMac 27'' 2017 RAM with MrMemory review - Wim Arys
Amazon.com: OWC 32GB (4x8GB) 2400MHZ DDR4 SO-DIMM PC4-19200 Memory Upgrade Compatible with 2017 iMac 27 inch with Retina 5K Display (OWC2400DDR4S32S) : Everything Else
New iMac 21-5-inch 4K Model is More Upgradeable Than Past Machines | Digital Trends
Install memory in an iMac - Apple Support
16GB PC4-19200 RAM for Apple iMac Mid 2017 - 27 Inch Retina 5K MNE92LL/A - MNE92xx/