Alternative reading light (change on Conrad2468's design).

Changes:

• Faster to print
• Lighter to wear
• Clips onto more glasses

Works well with white led.

The battery is a CR2032 Lithium battery. It is possibly the most common type of lithium battery.
You may get them at a pharmacy or online: http://www.google.nl/search?q=CR2032

I recommend a white led. It officially requires over 3V.
The led will work but not at full strength, preventing it from overheating (no resistor required!) and it uses less energy. We found out that the led gives enough light to read, more light would actually be unpleasant.