Cheap way to add a light to the mailbox

The author basically cuts a hole and glues a solar lawn light onto the mailbox.  Not a bad idea, I was at first trying to figure out why the side and not the top, when it dawned on me that maybe he did it partly cause its flat on the side (better seal), but also cause the sun rises on that side, and sets on the other (so the light is more likely to turn on at dusk).

http://www.instructables.com/id/Solar-Mailbox-Light/