Download po file from CiviCRM.org > Download. If your server support php-gettext, and have such locale in Linux, you should consider using native PHP-gettext solution. Read more about how to setup here: http://wiki.civicrm.org/confluence/display/CRMDOC41/CiviCRM+Localisation#CiviCRMLocalisation-Usingnativegettextsupport