Nav lights.
The only nav lights that I am finding are on the front wing tips of each wing and nothing on the tail feathers (!).
I'm using radio shacks #22 gauge wire, two wires twisted together with a vise and hand drill.
I connect some LED's on one end of the twisted wires and a male extension plug on the other.
Since the nav light area is large, I used two LED's soldered together and one of the wires on the LED was bent into a circle and a #0 screw was used to hold it inside the nav light cavity.
The ARF comes with solid gel coating where the nav lights are located but has nice rivet/panel detail.
I first used an old canopy clear plastic, held the plastic on one side, used a heat gun to soften the plastic and then wrapped the plastic around the nav light area.
Each side of the plastic was not completely flush with the edge of the wing, so I drilled/screwed one side down using #0 screws and then re-heated the corners and was able to smooth the two edge corners to conform to the edge of the wing.
I then used a razor saw to cut out the nav light area and then sanded the edges smooth.
I used two LED's (#RL5-G8045 from superbrightleds.com).
The LED's need two AAA batteries in series which were mounted in radio shacks single battery cases and screwed to a piece of 1/8" thick ply. The batteries will be mounted on the receiver tray and one wire routed to the service panel where an on/off switch is located.
They shouldn't need charging very often since LED's current draw is very low.
After the LED's were mounted, I drilled and screwed the clear cover to the wing using #0 screws.

pic 1/2:
Nav clear cover from an old canopy.

pic 3:
The center was then cut out and the two LED's were screwed in place.

pic 4:
The other end bound with the aileron and flap extensions.
The wing is hollow so routing the wires through the wing was easy.

pic 5:
Radio shack battery cases in series.

pic 6:
Bench test of LED's.