Timetec 8GB DDR4 2666MHz PC4-21300 Non-ECC Unbuffered 1.2V CL19 1Rx8 Single Rank 288 Pin UDIMM Desktop PC Computer Memory RAM Module Upgrade (8GB) at Amazon.com
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