The Adafruit 1351 2-Way 2.1mm DC Barrel Jack Splitter Squid
Double up your power adapters with this wonderfully simple 2-way power jack splitter. All you have to do is connect a standard 5.5mm/2.1mm sized plug into one end, and behold, two identical plugs to use! We like the rugged molding on these adapters, and they're really handy when you have a project with multiple pluggable devices.