Birth Certificate For Naturalized Us Citizen

I have run into a situation where my original birth certificate is necessary. I am a Vietnam born refugee child and arrived in the US with my parents when I was a baby, presumably on a refugee visa. From what I was told my original Vietnamese birth certificate was destroyed during the war. Somehow I became a naturalized US citizen when I was 7 years old and have been able to live my entire life without ever having to submit an original birth certificate as there were always acceptable alternative documents, until now. From what I understand I can request a copy of the BC through the provincial Justice department, however I am missing information such as the location of birth and my parents' name in vietnamese. They are deceased and I have only known their English and Chinese names. I do not have the whereabouts of any relatives in that area as my parents were themselves displaced to Vietnam due to the Khmer Rouge situation in Cambodia. I'm at a loss as to what steps to pursue to obtain my birth certificate.