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
How To: Upgrade 2017 5k iMac RAM to 64GB & Saved $840 | 2018 - YouTube
parts-quick 8GB (2 X 4GB) Memory for Apple iMac 27" 2017 5K Retina Display RAM Upgrade - Walmart.com
Timetec 16GB Compatible for Apple 2017 iMac (27-inch w/Retina 5K, 21.5-inch w/Retina
OWC 64GB DDR4 2400 MHz SO-DIMM Memory Upgrade Kit
Install memory in an iMac - Apple Support
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
How to upgrade RAM in the (Mid 2017) 5K iMac and save up to ~$900 [Video] - 9to5Mac