Thanks!

I should have searched under "trail" in retrospect.

Thinking that the tartan appeared to be based on the St Andrews saltire flag I searched using "andrews" and "saltire" and those likewise didn't do the trick.

That "pipers trail" tartan is essentially a two-colour blue & white tartan, and when paired with doublets that are dark blue with white piping, and dark blue Glengarries, and blue bag-covers, makes for a very uniform uniform.