A small option for a power source.  Used for powering less than 20 lights.  The attached connecting cable is about 6 inches long.

Small, flat power source!

There is a built in sliding on / off switch to power the lights on and off

Open the holder to insert two CR2032 batteries (not included)

ALWAYS insert and remove these lights by holding the plug.  Removing the lights by pulling on the wire can result in damage.  To remove the light from a port, grip the plug with your finger nails and pull.