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
Cisco 32GB DDR4-2666-MHz RDIMM/PC4-21300/Dual Rank/x4/1.2v » Vista IT Group
VENGEANCE® LPX 32GB (1 x 32GB) DDR4 DRAM 2666MHz C16 Memory Kit - Black