OWC 8GB PC21300 DDR4 2666MHz SO-DIMM Memory Compatible with Mac Mini 2018, iMac 2019 and up, and Compatible PCs (OWC2666DDR4S08G) at Amazon.com
Crucial 8GB Single DDR4 2666 MT/s (PC4-21300) SR X8 SODIMM 260-Pin Memory - CT8G4SFS8266 at Amazon.com
OWC 16GB (2 x 8GB) PC21300 DDR4 2666MHz SO-DIMMs Memory Compatible with Mac Mini 2018, iMac 2019 and up, and Compatible PCs (OWC2666DDR4S16P) at Amazon.com