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
Install memory in an iMac - Apple Support
How To: Upgrade 2017 5k iMac RAM to 64GB & Saved $840 | 2018 - YouTube
Install memory in an iMac - Apple Support
512GB 4X128GB NEMIX RAM Memory for Apple iMac Pro 27-inch Late 2017
The New 2017 iMac: Notes & Tidbits on RAM - The Mac Observer
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
Adamanta 16GB (1x16GB) Memory Upgrade Compatible for 2017 Apple iMac 27" Retina 5K Display DDR4 2400MHz PC4-19200 SODIMM 2Rx8 CL17 1.2v Dual Rank RAM DRAM at Amazon.com