CAL Lighting 1.5 in. White Plastic Outlet Adaptor HT-277-WH - The Home Depot
L-Type Track Lighting Connectors for L-style Single Circuit 2-wire Style Track System Pendants Lightolier Compatible Track Adapters Black Rail Head Track Accessory for 110V Pendant Spotlights 6 Pack - Amazon.com
Volume Lighting 2720-6 White Track Light Cord and Plug Connector - LightingDirect.com