OWC 32GB (2 x 16GB) PC21300 DDR4 2666MHz SO-DIMMs Memory, Compatible with Mac Mini 2018, iMac 2019 and up, and Compatible PCs, (OWC2666DDR4S32P) 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
Samsung 32GB DDR4 2666MHz RAM Memory Module for Laptop Computers (260 Pin SODIMM, 1.2V) M471A4G43MB1 at Amazon.com