According to Steve Roud's index, there is a version in the Glenbuchat manuscripts, which Emily Lyle published in Scottish Ballads, and which is also presumably in Buchan and Moreira's edited volume of Glenbuchat materials. I don't have easy access to this version, but someone on the list must.

That pushes the date in oral tradition to about 1818, and we aren't that far from when John Reilly's Mother would have been born--within a century, anyway.

If anyone had that text available to post, that would help. In a pinch I can go into the vast library stacks at work for a copy.