Looking for help to find Polish passport #poland

Sandra Lion

My name is Sandra Lion and I'm from Argentina. My mother is trying to get the Polish citizenship from his dad, who came from Poland in 1923, when he was 5 years old. He came with his mother and sister. He became Argentinean citizen after 1951, so my mum could apply for it. She has all the papers she needs except for his passport, or his grandomther passport (as her dad was so young he could probably be on his mother passport).
I asked for information on different Polish archives such as Archiwum  Główne Akt Dawnych, Archiwum Państwowe w Radomiu, Archiwum Akt Nowych but they all said they don't have a copy.
Do you have any other clue where I could look for my grandfather's passport or his mother's? 
I very much appreciate your time for reading this!
Thank you!!!
Sandra Lion

Join main@groups.jewishgen.org to automatically receive all group messages.