This is somethink I wanted to do for some time.
Finally I ordered it on eBay and it arrived yestrday.

It cost about 2,5 dollar one. You get the projector, magnet and tape.
Just tape it to the door, the magnet to the frame and here we go.



I really like it and the light is quite strong.
Easy to do it, easy to remove it.
If you want, I can add the link the eBay.