Because maps are copyrighted material, it is not easy to find free stuff.
Have a look on Mary Sauers ClipArt-page, whether you can use one of her
maps: http://msauer.mvps.org/graphics.htm.

If you are willing to pay some Euros for a good map, have a look at
www.presentationload.de (in German), click on "Landkarten & 3D-Globen" (maps
and 3D globes) in the left navigation pane, the rest is self-explanatory
with pictures.

Best regards,
Ute