Actually I found some single 18650 battery holders (at a different site) [Gino Black Battery Storage Box Case Holder for 3.7V18650x1 Batteries] that would be PERFECT to solder on to these!
However as others said the Miller ML-102
SKU 1158900 is a pretty nice alternative
P.S. The TP4057 setup is the EXACT same chips that are in the Xtar MC1 (I broke the micro USB connector on mine, opened it up, found the number on the IC's (56b8) (which cross references to the TP4057) and soldered it back down saving it.
Only thing the miller doesn't have that the MC1 has is the sliding battery terminal which lets you charge anything from an 18350 all the way to an 18650 and everything in between
Edited on 1/17/2014 at 9:37 AM. Reason: