[Ger-Poland-Volhynia] Search for ancestors settled 1821 in Wincentowo in the Pultusk area

[Birgit]

Hello,
my ancestors were German settlers of evang.-augsburg. confession and lived  
1821 near the river Narew in Wincentowo and surrounding area.  
Unfortunately the Protestant parish register of births at the Pultusk  
archive starts at 1843.
My question: Where should I search for my ancestors born in 1821? In the  
Roman Catholic church register for Pultusk? In the civil registration for  
Pultusk? Or in the Roman Catholic church register of Obryte which is  
closer to Wincentowo than Pultusk? Thank you for your help.
Birgit Jenning