LL Bean is now offering flannel shirts in the Leatherneck tartan, but considering the fact that over the last 13 years all of his postings have been to semi-tropical, tropical or desert climates, I figured he'd get more use out of a lighter weight kilt than a flannel shirt.
I have one of LL Bean's tartan shirts in the Maine State Tartan, and it is not flannel -- a cotton blend, if I remember correctly. It is in the "Americana" series with the Leatherneck and other armed forces tartan shirts.

Cheers,

Todd