HP 8GB (1x8GB) Dual Rank x8 DDR4 2133 MHz 288-pin DIMM RAM Module SDRAM (726718-B21 ) at Amazon.com
Amazon.com: Crucial 8GB Single DDR4 2133 MT/s (PC4-17000) DR x8 Unbuffered DIMM 288-Pin Memory - CT8G4DFD8213 : Everything Else
A-Tech 8GB Replacement for HP 797258-581 - DDR4 2133MHz PC4-17000 ECC Unbuffered UDIMM 2rx8 1.2v - Single Server Memory Ram Stick (797258-581-ATC) at Amazon.com