I have a gentoo box and the portage server I use is a partial one. That means that it has only limited (only essential) files on it. In case I have to install some package not on the server I have to download the required files from somewhere else and place them in $DISTDIR. Well I have found an excellent site to download such files. Note that this is not an advertisment and I have no association with the site and I will like others to tell if they have a better site. And also the site has a nasty ad on it just ad-block it (in case u r using Firefox).
Site