SK Hynix 8GB HMA81GS6JJR8N-VK DDR4 2666MHz SO-DIMM Memory
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
SAMSUNG M471A1K43CB1-CTD 2666MHz Memory Modules (8GB, 1 x 8GB, DDR4, 2666 MHz, 260-Pin SO-DIMM, Black, Green) at Amazon.com