Southwire Quad Box 2-ft 12/3 2-Prong Indoor/Outdoor Medium Duty General Extension Cord in the Extension Cords department at Lowes.com
Sigma Engineered Solutions 1-Gang Gray Metal Weatherproof New Work Standard Box Extender Exterior Electrical Box in the Electrical Boxes department at Lowes.com
Arlington Industries Box Extender (2-Pack) BE1-2 - The Home Depot
KOLORS ADD ON POWER EXTENSION BOX WITH SINGLE USB 3 Socket Extension Boards Price in India - Buy KOLORS ADD ON POWER EXTENSION BOX WITH SINGLE USB 3 Socket Extension Boards online
BELL Extension Box: Aluminum, Gray, For Use With 1-Gang Electrical Box - 2DCW7|5406-0 - Grainger
E-tech 4 Socket Extension Box Board with Surge Protector Spike Guard Power Strip Extension Cord Flex Box Power Indicator (Red, 6 feet Long Cable, 240 Volts) : Amazon.in: Electronics
Gangable Box Extenders (2-Pack) at Menards®
DIY - Extension box to power your Equipments - YouTube