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
A-Tech 16GB RAM Replacement for Crucial CT16G4DFRA266 | DDR4 2666MHz PC4-21300 UDIMM Non-ECC 1.2V 288-Pin Memory Module at Amazon.com