have no clue, whats the mepis website look like?
Ive never had this problem, the distro I use(slackware) has a website with complete sources and pkgs for everything theyve done going back about 4 or 5 versions, plus a couple slackware package sites with ready to go packages of everythign else.
Im assuming mepis is debian based, so debian packages should work I would think.
might want to go here and poke around too, not sure if they have a mepis forum subsection or not:
http://www.linuxquestions.org