You can only do that at [url=www.surefire.com]Surefire[/url] or [url=www.batterystation.com]Battery Station[/url] or some place similar. Buying from them by the dozen will work out to about $1.25 ea. last time I bought from them. You will need them in quantity because run time will be about an hour per set unless you are running LEDs.

edit

I've switched to the Fenix Lx series. Their new L2D with a Cree LED will give you Surefire light & run time from a pair of AA.