Find missing father in Vietnam War

Find missing father in Vietnam War
I would like to find a German-American Staff Sergeant Harrill or Harrison who served in the 720th Military Police Battalion, 89th MP Group, 18th MP Brigade at Long Binh Post, Vietnam from 1968 to 1970.
During this time, Harrill or Harrison, about 23 years old, was acquainted with a Vietnamese girl named Le Thi Ngoc, commonly known as Lee Lee, who worked at Cafeteria of the III Corps in Bien Hoa.
Harrill / Harrison went to the United States and Lee Lee was pregnant with Harrill / Harrison and gave birth to a daughter.
Today this girl asked me to find her biological father.
For those who have served in the military during the time that you know or have information about Harrill / Harrison please contact us 206-724-9947 or email vpham_egs@hotmail.com.
Thanks, Vincent Pham