Ich habe es gefunden, "firefox-pgo-i18n" liegt im adslgr64 Repo.
[adslgr64]
#The Hellenic (Greek) archlinux unofficial repository with many interesting packages.
Server = http://adslgr64.tiven.org/archlinux/x86_64
oder
[adslgr32]
#The Hellenic (Greek) archlinux unofficial repository with many interesting packages.
Server = http://adslgr32.tiven.org/archlinux/i686
Grüße