You may not be able to use apt-get without internet, but as I mentioned in my previous posting, you can
install packages without internet access if you use dpkg.
Anyway, you can use apt-cache depends package
is the name of the package) to find out a package's dependencies. I'm not aware of any terminal command that also produces a full url, but I wouldn't be surprised if there was one, because that information could be gathered from the sources.list and the files in /var/lib/apt/lists (the files with names ending in _Packages).
Unless someone else comes up with the name of the command you're after, you could use apt-cache show package
for each item to get the contents of the Filename keyword and append that to the url of the repository to retrieve the file.
E.g. if you wanted the Bless hex editor, the Filename would be pool/main/b/bless/bless_0.6.0-4_all.deb
. The url of the main Debian repository is http://ftp.debian.org/debian/
so you could browse to http://ftp.debian.org/debian/pool/main/b/bless/
and download the right deb file.
Packages can also be searched on http://www.debian.org/distrib/packages
(the "normal" Debian packages, anyway). Those pages should also tell you about any dependencies and provide links to them.
Edit: Just out of curiosity I googled "find package url Debian". Found this: http://linuxers.org/article/find-downlo ... ng-apt-get