PNY Performance 16GB DDR4 DRAM 2666MHz (PC4-21300) CL19 (Compatible with 2400MHz or 2133MHz) 1.2V Desktop (DIMM) Computer Memory – MD16GSD42666 at Amazon.com
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