3 PCS Waterproof Junction Box, 3-Pole IP68 Connector, External Sleeve Coupler, Ø 3.5-10 mm (Black, PA66), Outdoor Cable Connector. Outdoor waterproof Junction Box Connector: 2 way M16 plug connector, Cable Range: 3.5-7mm /7-10mm, 2 or 3-pin cables, suit for most usually power cord.
eBay