Kingston KTD-PE426E/16G Memory 16GB DDR4-2666MHz ECC Module at Amazon.com
Crucial 16GB DDR4 SDRAM Memory Module - for Notebook - 16 GB - DDR4-2666/PC4-21300 DDR4 SDRAM - CL19-1.20 V - Non-ECC - Unbuffered - 260-pin - SoDIMM (CT16G4SFS8266) at Amazon.com
Kingston 16GB DDR4 SDRAM Memory Module at Amazon.com
OWC 32GB (2 x 16GB) PC21300 DDR4 2666MHz 260pin SO-DIMMs Memory Ram Module, Compatible with Mac Mini 2018, iMac 2019 and up, and Compatible PCs, (OWC2666DDR4S32P) at Amazon.com