Naka palit ko before sa Modern Teknica along Magallanes St. downtown. (between F. Gonzales and Plaridel sts.) About 40 to 60 pesos each (not sure).
But there is a cheaper alternative.
Just buy one of those cigarette lighters with built-in flashlight. It has a superbright blue led. Barato pa. Only 10 pesos ra sa mga Chinese bazaars in downtown.
Hope this helps.