Hmm...I wonder if the name refers to the group of Royal Marines from the HMS Repulse and Prince of Wales that joined up with some Argyll-Sutherland Highlanders in Malaya in 1941 and fought the Japanese? They are sometimes called The "Plymouth Argylls". If that is the case, then I would say the Government tartan that the A & S wears would be appropriate, and fairly easy to obtain.

T.