With your assistance I have found my Grandfathers name on the Jewish Gen database! I found it in the polish Birth records for Hrubieszow!
It says there he was born on 1902 (which fits his age when he died) and his name is spelled Jojna Bigler (not Jona) - but I remember very clearly that my grandmother rest her soul used to pronounce his name like that.
I also found many many records of Bigler Jews in Hrubieszow including births, deaths and marriages...
But I can not see a copy of his orginal birth record - I wonder how I can get it? Because I really want to know how all the biglers in the records are related! and who were the parents and who were the siblings.
I will try and see if the database manager can help me