Hynix 16GB DDR4 PC4-19200 2400MHZ ECC REG DIMM Model HMA82GR7AFR8N-UH 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
Corsair CMK16GX4M1A2400C14 Vengeance LPX 16GB (1x16GB) DDR4 DRAM 2400MHz (PC4 19200) C14 Memory Kit - Black at Amazon.com