Not a recommendation or endorsement but:
simply do an ebay search for "magellan explorist 500 battery charger"
Lots of dealers selling for less than $20 for 2 batteries and a charger. If you get a charger with the USB receptacle on it, you can use the data cable to charge the battery without removing it from the unit.
Secondly, stay away from the AAA holder unless you need it for an absolute emergency. With Alkalines, it might last 5 hours on the lowest backlight setting, much less on rechargeables and much less at a brigher more readable backlight setting. The battery pack is rated for 14 hours on low and is quite a bit less on high, but still at least double that of AAA's.
does anyone in the room ahppen to have the actuall gps unit for sale im looking for the magellan explorist 500 please get ahold of me