Searching for Marriage date of great-grandparents

I am looking for the marriage date of my great-grandparents:

James Findlay to Sarah McNeill Small, approx mid 1840's

Sarah was previously married to David Small who died late 1830''s or early 1840's.

The McNeills lived in the Ballynahinch area.

All I know of the Findlays is that they lived just south of Belfast so am assuming they were from the same area as the McNeills.

Sarah's parents were John McNeill and Sarah Catherine Murray who left Ireland for Canada sometime between 1847 & 1849.

James and Sarah Findlay followed them to Canada in 1853.

They all settled in Bristol Mines, Quebec, Pontiac County

I will be visiting the Belfast area this coming September.