SAMSUNG M471A1K43CB1-CRC 8GB DDR4 2400MH Memory Module (8 GB, 1 x 8 GB, DDR4, 2400 MHz, 260-Pin SO-DIMM) 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
Crucial 8GB Single DDR4 2400 MT/s (PC4-19200) DR x8 SODIMM 260-Pin Memory - CT8G4SFD824A at Amazon.com