Certified Chinese to English translation of birth certificate & immunisation records

I need a certified translation of my birth certificate and also my immunisation records for a US immigrant visa.

Job involves:
1) Accurate translation of birth certificate (approximately 100 characters)
2) Accurate translation of immunisation records (approximately 300 characters)
3) A letter from the translator certifying the accuracy of the translation and your competence in doing the translation (backed up by appropriate qualifications and/or membership of professional association)

Fully fluent in Chinese myself - but prefer to use a third party to avoid conflict of interest issues.