In this way the battery can be easily installed near the hub of a bicycle wheel to feed LED lights fixed on spokes or on a crash helmet (I will illustrate these applications in other Instructables).
I used a very common plastic (PE) cap of a water bottle that has an inner room that fits the dimensions of a CR2016 or CR2025 up to a CR2032, and the back of another cap to seal the battery inside, welding the PE parts with the tip of a soldering iron.
The switch was pinned on the side of the main cap and electrical contacts to the battery were made with jagged washers and some pieces of a PC flat cable for the wiring.
The outer rim that results can be used to obtain at will buttonholes/holes to install the kit on the final destination using plastic tie wraps or screws.
Step 1: Some of the things used
It is better to use caps for still water because they don't have reinforcement ribs on the inside or bulges as the ones for sparkling beverages have. This reinforcement is not needed here because of the small weight of the battery (about 4 grams) and mainly not to waste room inside the housing.
You can chose the colour of the caps following your personal taste, but since you will have to connect pieces together, it is advisable to make a welding test to see if the colour charge doesn't give problems.
For my personal choice and to avoid any issue I used white-transparent caps as shown in the picture.