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
Timetec 4GB DDR4 2133MHz PC4-17000 Non-ECC Unbuffered 1.2V CL15 1Rx8 Single Rank 260 Pin SODIMM Laptop Notebook PC Computer Memory RAM Module Upgrade ( 4GB) at Amazon.com
Micron MTA4ATF51264HZ-2G6E1 Non ECC PC4-2666V 4GB DDR4 at 2666MHz 260pin SDRAM SODIMM Single Kit Laptop Memory - OEM at Amazon.com