I'm guessing that by "pattern" you mean a pattern like for making a shirt or jacket, giving the shapes of the various pieces of fabric that are cut out of fabric yardage and sewn together to create the garment.
Thing is, Balmorals and Glengarries aren't made like that. There are no seams because the hat is knit in one piece.
So a "pattern" in the sense of a Butterick or McCall's pattern cannot exist.
There is a newer type of bonnet, invented during World War One, the army dubbed the Tam O'Shanter, that is cut out of fabric yardage and sewn together. It's made from the same cloth the military wool serge jackets are made of.
Here's a newspaper article announcing its introduction. (The article calls the new hats "Balmorals" but as far as I know the army has always called them Tam O'Shanters. Also the tourie or pompom is missing.)
I have seen inexpensive crude-looking imitation Glengarries cut from cloth yardage, made in Pakistan, sold at Highland Games and in tat shops on The Royal Mile.
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