LEGO PART 58118 Wire with Brick 2 x 2 x 2/3 with 1 x 2 Studs and Power Functions and 9V Connectors, 50cm, One Light Bluish Gray End | Rebrickable - Build with LEGO
LEGO Electric Wire (4.5v) 96L with Light Gray 2-prong Connectors | Brick Owl - LEGO Marketplace
Connectors similar to Lego "wire and plate" pieces - Electrical Engineering Stack Exchange