Sir Alexander Mackenzie

Sir Alexander Mackenzie’s Canadian Daughter
Hello!  I’m following a lead regarding Maria Mackintosh (sometimes Brown) being a natural daughter of Sir Alexander Mackenzie; she was baptized as such in 1805, only a few years before he moved to Avoch permanently.  I believe she was cared for initially by Sir Alex’s sister Margaret (Mrs. James Dowie) before she married Robert Munro.  I wonder if there are any resources you might connect me to in my search?  I’d certainly appreciate any help you could provide.  Thanks for pondering.  Regards – S.