Got it. I found just the right font. And free, too, which wasn't that easy.
This is the so-called DIN Schablonierschrift. The stencil type font according to the German Institute for Norms. It is very commonly seen on shipping containers but also on planes and fighter jets. Fits perfectly for my luggage.
You can find it here:
http://www.sendung.de/dinschablonierschrift/
For mac and pc.
I also thought of another possibility. Instead of stenceling out a self-adhesive tag and using wet paint on the bag directly. One can stencil out an ordinary piece of paper. Glue a day-glo duct tape stripe to a piece of glass (couch table for example) from which it will easily detach. Then put the stencil on the day-glo duct tape. Fill in with black marker and glue duct tape to bag. This way it is super easily removable if you don't like it or you are too scared to spray or paint the bag's material itself.
Now to find the right color. I imagine something that is a bit rubbery, say on a latex base. That should stick well but could also be peeled of or dissolved with alcohol or similar dissolvant.
Till