Finally I finished the battery box. The previous version was far from good, the O-Ring was not held by anything when the box was open, so it was very easy to loose it. The new version has this problem fixed, I didn't have much time to test how much waterproof it is, but a brief test in the kitchen sink was successful.

Also I'm building another two lamps for my friends, the green version look pretty awesome, I guess I'll try more different colors next time.