This works for me outside with the Hubbell:

2-Gang Weatherproof Deep Box, Five 1 in. Threaded Outlets, Gray (5389-0): https://www.amazon.com/gp/product/B003A4B9JO/

TayMac MX6200 RaynGuard Extra Duty Metal Weatherproof in-Use Cover, 2-Gang, Gray https://www.amazon.com/gp/product/B001DKB3H0/

TayMac CP4100S Metallic Closure Plug Weatherproof Accessories, 1-Inch Per Polybag, Gray https://www.amazon.com/TayMac-CP4100S-Metallic-Weatherproof-Accessories/dp/B008KNYSI4/

The cover comes with a plastic faceplate for a single NEMA 14-50. I added some silicone sealant to the plugs just to make sure.