Outdoor Electrical Box 12 x 10 x 6''D NEMA 4X Enclosure Steel Box, Waterproof & Dustproof Outdoor/Indoor Lockable Electrical Junction Box, with Mounting Plate

I would probably just enclose the receptacle in a lockable electrical box of some sort. You don’t have to use a weather proof electrical box to house the actual receptacle if you choose an NEMA-3R or higher