I'm guessing you don't want to invest too much money for this rechargeable set-up. The Ultrafire WF-139 is a good, basic charger. You'll just need a 15mm Charging Spacer so the WF-139 can be used to charge the RCR123 cell you'll be using.
With the WF-139... You have to keep an eye on it. This is not the sort of charger where you can go to bed, and just leave the cells charging overnight. This charger doesn't stop charging once the cells are full. You have to watch for the light on the charger to turn green, and turn it off right then. When you do remove the cells from it, it's best to wait a few minutes before installing them into your light.