An AC adapter should'nt be too much trouble to add...its just using 6 volts DC. Someone correct me if I'm wrong but, it seems like you could wire in a 6v 200mah or greater DC wall wart in place of the batteries.
All the other parts are radio shack/junk box specials... a battery holder, euro terminal strip, spst switch, and led holder. Maybe a velcro dot or 2 to hold the parts in place in the control panel. Its possibly 8-10 dollars worth of parts. (assuming you already have a joystick)