>Good to know - but who sells those?

Depends on where you live. Here in Germany we have some big electronic stores who sell those parts. Such a 7809 doesn't cost much, about one dollar/euro or two.

If you can measure resistance, test the tree solderpoints for shorts. There is a chance of having a defective 7809, but this happens only once in a blue moon. Don't count on this.

Rolf