A friend gave me a package of printable magnetic sheets (thanks Anne). I tried to print it, but that didn't work very well. So I decided to do an experiment and combine it with felt. It's very easy and I tried to make a little tutorial.
All you need is, some felt fabric, a pattern you like, glue (I used photo glue, because I didn't have anything else at the time, but I think it's better to use, general glue or textile glue, nevertheless the result with photo glue was o.k.). Just glue a little piece of felt on the magnetic sheet and cut out the form...ready is your felt magnet!