Ugh, sorry about the Puzzler post... Definitely left logged in and I didn't notice.
Anyhow, I'd say the best solution would be the regulator but if you don't have one, another (possibly cheaper) solution could be made with appropriately rated zener diodes.
EDIT: Found some decent diagrams and an explanation of how to do things the zener diode way, as well as how to do it with regulators (just keep hitting next slide):
http://www.mines.edu/Academic/course...t11/sld005.htm