For right now, you can save the bonus pack to disk and then copy it over.
In the general case, we are not going to be providing separate install executable for updates. You need to install Stardock Central (and probably the game itself) on a computer that does have access, download the update, archive the game, and copy the archive to the computer without access, then restore it on the target computer with Stardock Central.
If it's the first time you've done this, you'll also need to activate the product. When connected, this is done seamlessly. When not, it involves sending an email with a signature blob to Stardock, receiving a signature file in return, then putting that file in the correct location on the target.
This is why we highly recommend an Internet connection for updates.