Where can I get an Affidavit of Competency to Marry in the US?

I am getting married to a Japanese national and need to get an Affidavit of Competency to Marry, but I need to get it notarized here in the US before I go to Japan. Where can I get this done, as I would imagine it needs to be done by some government official of some sort? Also, where can I get a translation of my birth certificate, without having to pay some crazy amount of money.