OWC / Other World Computing 64GB (2x 32GB) DDR4 2666MHz SO-DIMM Memory Upgrade OWC2666DDR4S64P
V-Color 64GB (2 x 32GB) ECC SO-DIMM DDR4 2666MHz (PC4-21300) for microservers, workstations, Networking Platforms and Embedded Systems 2Rx8 CL19 1.2V (TES432G26D819K-VC) at Amazon.com
VENGEANCE® Series 64GB (2 x 32GB) DDR4 SODIMM 3200MHz CL22 Memory Kit