Buy LED strip on Amazon (paid link)
LED can be found in almost every gadget we use this days.
LEDs are cheap and simple to use for endless list of projects.
On this page you will find some projects I did with LED, mostly for aquaruims.
Backlight for Aquarium
DIY Dual LED Lights
DIY Aquarium LED Light
LED Light Holder
LED USB Light DIY no soldering
How to find corresponding ends of wires