Amuro:

Someone elsewhere mentioned that instead of gluing the light staff down, to use piece of steel rod in the base, and then a magnet under the styrene so that its easily placed and removed.

But I think Crunchie's idea is best... use a dummy partial post in the spot when you atren't using the light, and then just pop it out, and pop the other one in. You may have a problem with the post staying in place, but a bit of something sticky on the inside of the post-hole might cure that. Carmatic swears by blu-tac...