Searching for Josef and Veronika Uma 1820 Bohemia

We have been searching for 20 years for documentation on Josef Uma and Veronika Stransky Uma who sailed to Quebec in 1854. On that date the family brought 4 sons, Josef, John, Francis and Wilson. Veronika was pregnant on the voyage and lost the baby girl. Family conversation leads us to believe Josef was born in Pribra, Böhmen 1815. We do not have birth, christening/baptism, or marriage records on Josef, Veronika or their sons. Upon arrival in Iowa, they began using the name “Omer” and there have been suggestions that they came from St Omer, France but no records have been located on that. Please help us find any record on Josef and Veronika Uma and sons.