Hynix Original 64GB (4x16GB) Laptop Memory Upgrade Compatible for HP Zbook 15 G3 Mobile Workstation DDR4 2133Mhz PC4-17000 SODIMM 2Rx8 CL15 1.2v DRAM Notebook Adamanta at Amazon.com
4gb ddr4-2133mhz sodimm - new | Newegg.com
A-Tech 8GB Module for HP 15-bs091ms Compatible DDR4 2133MHz PC4-17000 Non-ECC SODIMM 1.2V - Single Laptop & Notebook Memory RAM Stick (ATMS397715A34065X1) at Amazon.com