Timetec 32GB KIT(2x16GB) Compatible for Apple 2017 iMac (27-inch w/Retina 5K, 21.5-inch w/Retina 4K / Non-Retina 4K) DDR4 2400MHz PC4-19200 SODIMM MAC RAM Upgrade for iMac 18,1 / iMac 18,2 / iMac 18,3
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
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 32GB (2x16GB) 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
Apple iMac (27-inch, 2017) review: Apple doesn't mess with success - CNET
Amazon.com: Late 2017 Apple iMac Pro with 3.0GHz 10 Core Intel Xeon W (27 inch, 32GB RAM, 1TB SSD) Space Grey (Renewed) : Electronics