Halex 1/2 in. Strain Relief Cord Connectors (2-Pack) 21692 - The Home Depot
ETi Linking Cord Connector - Connect Two 5ft. Linking Cords Together - Works with Specific Compatible Fixtures Listed 91000010 - The Home Depot
Arlington 1/2" Non-Metallic Cord Connector .385" to .750" Cable Range
HQRP US Cord Connector NEMA L5-30P Locking Plug 30 Amp, 125 Volt, 2 Pole, 3 Wire | eBay
Universal Power Extension Cord Cable Strip (1FT) - NEMA 5-15R to NEMA 5-15P Wire Connector Socket Plug Jack Outlet Power Strip Liberator Space Port Saver Extender - Black - Walmart.com