More digression-
Until fairly recently, the usual name applied to Metis by white Canadians was half-breed; white would-be militia men in Alberta still celebrate the victory over the Metis at Batoche and the Metis failure in the "Insurrection of 1885." (The Gatling gun was first used against them, according to history.
Metis in Montana (and a fairly large number in Minnesota) are two of the disintegrate remnants. Those in Montana had moved there with Dumont. Many who traded with Red River carts operated out of Minnesota.

The following website is maintained by the Metis National Council. It defines the Metis as a "distinct aboriginal people," something that Metis who are absorbed or in the process of absorbing into mainstream Canadian life, are trying to leave behind. If you read the material here, they estimate some 350,000-400,000 Metis in Canada.
www.metisnation.ca
Metis

The Scots-English-Indian mixture are mostly absorbed and steer clear of French-Indian Metis politics.

Unless you contact Bowen and find out that he had some specific tune in mind, I doubt that you will be able to find a "Baptiste's Lament."
I think it existed only in the mind of Bowen and his characters.