CMS 4GB (1X4GB) DDR4 19200 2400MHZ NON ECC SODIMM Memory Ram Compatible with Apple IMAC Retina 5K, 27-inch (2017) - C105 - Walmart.com
Apple Memory Module 32GB DDR4 2400MHz SO-DIMM (2x16GB) | The Summit
8GB Memory Upgrade for 2017 iMac 27-Inch
Amazon.com: OWC 8GB (2 x 4GB) PC19200 DDR4 2400MHz SO-DIMMs Memory Compatible with Mac Mini (Late 2018), 27" and 21.5" iMac (Mid 2017), and Compatible PCs (OWC2400DDR4S08P) : Everything Else
Apple Memory Module 16GB DDR4 2400MHz SO-DIMM (2x8GB) - Apple