ZERO worries treal512. it uses 4 18650 cells. (very common cells in this category) simply buy a 4 cell holder 4 cells and a charger and cut off and move the power wire to your new holder and cells.
done. should fit in the bag that came with it too. when my cells die this is what I will do. you can then buy whatever quality level cells you wish and replace every few years as needed.