These put me in mind of the flannels you'll find if you're ever lucky enough to visit O'Connells in Buffalo NY and get to rooting around in the drawers at the back of the shop. Old deadstock treasure that still has the O'Connell's, Lucas and Chelf labels.

Woof has mentioned these elsewhere, but I think this thread is worth a little bump as the shirts are due in. 
Just bought a flannel (Bean) and a Madras on US Ebay.  The shirts cost next to nothing but the shipping and customs charges, as per usual, drive up the total price.  Annoying but that's the price that has to be paid for 'Made In The USA'.  I saw a Gap shirt on Saturday that looked superficially fine but wasn't.  Turned it inside out and found the tell-tale collection of long, satiny feeling tags.

Just harking back to the Lucas Chelf recommendation, a shirt is hanging around on Ebay at the moment if anyone's interested.  'Purist' - but poly/cotton.  University stripe.  £40.  Boom Years but quite likely unappealing to many.