[KyleGoetz]

Originally Posted by allhailhata

Iｔ's a relatively new Bureaucracy.

Fine. Some sources do still kanjify 為.

For reference, the Angelic Salutation ("Hail Mary full of grace...") includes

Holy Mary, mother of God, pray for us sinners [now and in the hour of our death]

which is translated as

天主の御母聖マリア
罪人なる我らのために今も臨終の時も祈りたまえ

Remove the "now and in the hour of our death" and "sinners" and "mother of God" and you have

マリア、我らのために祈りたまえ

To keep that level of formality and "religious stiffness," I'd say

我らのために祈りたまえ

A more modern translation of the Angelic Salutation is

神の母聖マリア、
罪深い私たちのために
今も、死を迎える時も
祈ってください

which yields, for our purposes,

私たちのために祈ってください。

So, OP, I provide you with the definitive answer(s), taken directly from official translations:
1. 我らのために祈り給え
2. 私たちのために祈ってください

There is no question these are correct.