In reply to a post on r/vexillology:

You could take the historic flag of New England - variations on the English Red Ensign with a pine tree, and combine it with the Nova Scotia flag in the canton. Something like the first or second flag as depicted here:

http://www.midcoast.com/~martucci/flags/NEFlag.html

but with the blue-on-white St. Andrew instead of the red-on-white Cross of St. George.