you can't really convert and uncompress a DVD5 to DVD9, the data is not compressed but re-coded in bad quality and with some deleted files (end credit apparently, and probably some unuseful videos like logo at game launch).
you need the original DVD9 JP and US to make a proper DVD9 undub.
I guess that will be hard to find someone with the knowledge to do it, that game is old and the capable and interested users already did the work on it. they are probably not interested in doing it again.
Maybe new users might get an interest in doing it, but PS2 is not a current gen, so there's not a lot of users willing to do it here. maybe you'll get more chance on a specialized hacking/translating forum, like romhacking.net (I don't know if they do undub too).
but, maybe someone on gbatemp is ready to take on the challenge? finding both version is maybe the hardest, then you'll have to open each ISO and move files, rebuild the ISO and try.
Too bad the PSN version doesn't have language choice...