I have half sister in vietnam how do i find her born in late 60's during war?

so where do i go to find her in vietnam,i think she was born in saigon or near there. i have pics of her mom and baby.my dad told me on his death bed,of half sister there.dont have money to hire someone like P.I..dont have names of the mom or the baby.i think half sister might be in late 30s or early 40s.so im wondering if there name of my dad at a hospital where she was born or if she has my last name .so where do i goto look up names at hospitals online in vietnam so anyone can help.