Genealogy / need help finding someone in poland but don't have much information. [10]

I would like to trace my Grand Fathers birth certificate.

His name was Benjamin Marthinus Jewaskiewitz.

He was born in Polczyn Zdroj on the 21/04/1868.

He came to South Africa in 1870 at the age of 2.

He farmed in SA his Polish Birth Certificate was burned in a farm fire.

Who can I approach to trace his birth certificate?