In fact, the only way to get this file is when someone else runs initdb on their computer and sends the file to you via email or through some kind of hosting.
official way (documentation says):
, pg_hba.conf . default pg_hba.conf , initdb. ; . hba_file.
UPDATE:
pg_hba.conf (pastebin.com) ? , , PostgreSQL 9.1 Debian 6.