Been there, done that. Just need a 120VAC to 12VDC power source with enough amperage to handle the load.
FYI: Although it will be perfectly legal, as it would not be mounted on a moving vehicle, be prepared for unexpected attention from your local LEOs. It WILL draw their attention, and some LEOs are funny about ANYTHING that appears to imitate or usurp their authority.
I took mine down soon after the novelty wore off.