Game Gear Car Adaptor
From Sega Retro
The official Sega Game Gear Car Adaptor (カーアダプタ) is a accessory for the Sega Game Gear made by Sega. It power the systems by being plugged into a car's cigarette lighter, saving on batteries and being useful on long road trips. This adapter could also be used for the Sega Nomad which uses the same A/C port as Game Gear.