As for not being Catholic and, thus, not knowing exactly what they would say in a Catholic Church, that is fine. I appreciate the help regardless. I did find this translation on a blog that I read which is from a Catholic who is from Japan, so it might be the best bet. It is identical to your last "colloquial" version, except for the very last characters, which I assume is just meant to be translated as "Amen."
Catholic in Japan Blog --
恵み溢れる聖マリア、主はあなたとともにおられます。
主はあなたを選び、祝福し、あなたの子イエスも祝福さ れました。
神の母聖マリア、罪深い私達の為に、
今も、死を迎える時も祈って下さい。 アーメン。
_______________________
Megumi afureru sei Maria, Shu wa anatatachi to tomo ni oraremasu.
Shu wa anata o erabi, shukufukushi, anata no ko Iesu mo shukufuku saremashita.
Kami no Haha, sei Maria, tsumifukai watashitachi no tameni,
ima mo, shi o mukaeru toki mo inotte kudasai.
Amen.