A-Tech 8GB Module for HP EliteBook 840 G1 Laptop & Notebook Compatible DDR3/DDR3L PC3-14900 1866Mhz Memory Ram (ATMS266381B30845X1) at Amazon.com
HP EliteBook 840 G3 14" HD i5-6300U 16GB RAM 512GB SSD Windows 10 Pro | DN Printer Solutions, LLC
Upgrading Memory RAM in HP 840 G1 EliteBook, 840 G2 or 840 G3 - YouTube
Refurbished: HP Laptop EliteBook Intel Core i7 4th Gen 4600U (2.10GHz) 8GB Memory 500GB HDD Intel HD Graphics 4400 14.0" Windows 10 Pro 64-Bit (Multi-Language Support English / Spanish) 840 G1 - Newegg.com
8GB Memory for HP EliteBook 820 G1, 820 G2, 840 G1, 840 G2, 850 G1, 850 G2 RAM | eBay