Here is the X1 Power adapter I've been using for my X1. Works perfectly no issues. Hence you need a Xbox 360 Power supply NOT SLIM or the new ones. Only the Elites and younger.
http://www.amazon.com/Pythons-Suppl...sr=8-1&keywords=Xbox+One+power+supply+adapter
http://www.amazon.com/Pythons-Suppl...sr=8-1&keywords=Xbox+One+power+supply+adapter