iMac 5K Retina 27-inch Desktop 4.2GHz Core-i7, 16GB RAM, 1.03TB Fusion - Best Deal in Town Las Vegas
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
Memory Upgrades for 2017 iMac 27-Inch
How to upgrade RAM in the (Mid 2017) 5K iMac and save up to ~$900 [Video] - 9to5Mac
Apple iMac 5K Retina 27" Desktop - 4.2GHz Quad-Core i7 - 32GB RAM - 51 – The Refurbished Apple Store