This is a simple case for the Adafruit Micro Lipo USB charger. It snap fits together (or you can super glue it). It will hold the included power cable inside the case. The two holes on the front allow for the LED light to pass through if you use a darker color PLA. If you use white, the LED will shine through the plastic.
You can get the Adafruit charge here:
Just attach your own connector for charging your batteries. Connectors are available on Ebay or Adafruit.
I recommend a 0.2mm nozzle to print this as it does best to get the details for the snap fit. There is about 0.1 mm tolerances in the holes.
The LED light pass through holes re 1.85mm diameter. I actually inserted some clear PETG (T-Glase) that I had laying around as a "fiber optic". If you don't have any, the light shines through just fine.
Used a 0.2mm nozzle to get better resolution for the small part features; had issues with standard 0.4mm nozzle getting the part to snap fit together.
Small parts were lifting from the plate on my Prusa, so I disabled the fan for the first 15-20 layer which did the trick for me. Setting may vary for other users and prints.