Do you just have the one .vob file? Or do you have a complete dvd, with .vob, ifo and bup files contained in a Video_TS folder?
If you have a complete dvd this is simple to do with DVDShrink. You can find it here: www.mrbass.org It is free and there are guides to using the program at that site as well.
If you have just the one file, you can probably use it in an authoring program like DVDStyler or DVDAuthorGUI. In a Mac, I think you’d use iDVD or iMovie to make the dvd-video. Don’t worry that it is oversized at this point. You’re going to import it to DVDShrink and reduce the size there.
DVDShrink works in Windows and I believe there is a Linux version, but it won’t work in OSX. So that part would best be done on a PC.
The other option would be to use the .mkv file in AVStoDVD or DVDFlick or FAVC and go all the way to a finished dvd, of the correct size. Then burn to disk. All of these programs are free to use, but are PC only.
If you have problems with the authoring programs not liking the .vob file extension, rename it to a .mpeg extension.