It's not there because it's a
HUGE download.
The FAT32 partition that is used on USB sticks so people can add "stuff (charts, video, whatever) from a Windows system, will not handle files over 4GB...it just doesn't work.
If put Navigatrix on an 8GB stick there is no room.
If you use a 32GB stick, you are still limited to 4GB/file.
If Navigatrix is installed it's an entirely different situation.
Check out your options.
http://www.kiwix.org/wiki/Content for a broad range of offline content for the Kwix reader. Just remember the 4GB limit on FAT32.