I bought a Solar LED light that mounts on the top of the pole and does a good job lighting the flag. Ebay for about $30.00
It looks like a little spaceship on top of the pole and casts a light around the entire base area...
Great barn build. If you happen to get a small tractor with a box scraper you can weld a 2 inch receiver to the top. I did it to my box scraper and just add the hitch/ball when I need to move my trailor. It allows you to raise/lower the trailor and its very easy to back it anywhere you need to...