I attached the baptism record for the Martin MacDonald (who you described).
My 5G Grandfather Martin MacDonald (born ca 1755) who settled in Knoydart NS, is said to have a brother who settled in Glengarry Ontario. I have been unable to determine who this family was as of yet but have a number of records for various Martin MacDonalds from the area.
Let me know if you are able to open the attachment.
Hope it of use.