Thanks everyone for their advice. Instead of going down the CR123A/RCR123A route, I went with a pair of TrustFire LiOn 18650 (2400mAh) batteries and a new
ShiningBeam-S-mini-XP-G flashlight to match with my Pila charger. So far I love the amount of light the flashlight throws and its small size, although the switch could be improved.