I had the issue, that I had a machine completly without internet connection.
I solved it with this little Trick(s):
1st trick(good for you):
copy the whole apt-cache onto a empty usb-stick
$ sudo cp /var/cache/apt /media/your_username/name_of_usb_stick
then carry the usb stick to the other machine and mount the apt-cache on the usb stick to the apt-cache of your machine
$ sudo mount name_of_usb_stick /var/cache/apt
(you also can mount the apt-cache using nfs)
2nd trick:
(good if your machines are not similar)
First you install the same system on a usb stick(see here),
after that you go to a machine with internet connection an boot from your usb system
Here you fetch the packages using
$ sudo apt-get install --download-only program-you-want-to-install
then shutdown your pc and carry the usb stick to the machine without internet connection, now link the apt-cache on the stick to your apt-cache
$ sudo ln -d /media/your_username/name_of_stick/var/cache/apt /var/cache/apt
Then run
$ sudo apt-get install program_name
I hope this will help a few people