I built a Raspberry Pi 400 with 8GB of RAM. : r/raspberry_pi
Amazon.com: Vemico Raspberry Pi 4 Model B 4GB Set RAM 4GB Base Starter Kit with SD Card, Heatsinks, HDMI Cable, Power Supply, Black Case, Reading Card Device, Screwdriver : Everything Else
DeskPi Lite Case Full Kit with Raspberry Pi 4 Board - 2GB RAM / Q3 Pow – DeskPi Store
Amazon.com: RasTech Raspberry Pi 4 8GB Starter Kit with 32GB Micro SD Card, Power Supply with ON/Off, Case, Cooling Fan, HDMI Cable, Card Reader, Copper Heatsink, Screwdriver : Electronics