Death records for Sarah Jane McComb parents?

Hi i was just wondering if anyone could help me find death records for my 3x great grandparents Joseph McComb and Elizabeth McComb could also be spelt McCombs elizabeth’s maiden name was Boyd they married on the 25 May 1865 think it was registered in magherafelt or londonderry and they had a few children and one of them Sarah Jane is my 2x great grandmother i know when she died so i was just trying to figure out possibly when her parents died as i haven’t been able to find their death records from one of her daughters who went to australia and remarried in 1912 she has them both down as deceased so it must of been some time before then that they died any help would be appreciated thank you