The debian directory you should get bokomoko as well through the standard debian toolchain. Please check the documentation for the "apt-get source" documentation for details.
A debian directory(http://tech.visser-scully.ca/) is available so that you can build your own packages. Download and unpack in your top Navit source directory. Build a .deb file by using fakeroot ./debian/rules binary after running the initial autogen and configure at least once. The .deb file will appear in the directory above where you are. This works best after you have done at least one build using the full set of commands above.