Since Don was born before 1900AD, his Birth detailscan be traced from Colombo Archives if you roughly know his birthdate. His parents' names and 1881 census details could be used to trace where they lived in Colombo. Since Sri lanka has conducted census every 10 years since 1871, most probably, the information are available for reference at the Archives. There are agents in Colombo who woulddo this for you for a fee. I have no idea as to what they will charge though.