Same goes for my AA and AAA batteries. I use Eneloops, and it came with its own battery case to make storing easier. However, I lost the case and my batteries now lay scattered inside the camera bag. I browsed through the web and found someone sells battery case for Rm15. Quite expensive for a piece of plastic. Then, something came up, and I made myself one! I wonder why I didn't think of this earlier.
What do you need?
1. The clear disposable plastic battery holder that came with your batteries when you buy at shops - Ni-CD, alkalines or normal batteries have those.
2. A small piece of corrugated plastic sheet, cut that to match the battery holder size. You can use hard plastics too.
3. Binding tape.
4. Adhesive velcro straps. I got those from Daiso.
The procedures are pretty straightforward. Just put binding tape at one end of the corrugated plastic sheets, and adhesive velcros at the other.
Finished!