Thanks for the inspiration Robbie.
I had actually purchased a set of lovely Trico Aeramic 285 mm chrome (stainless) blades that suit a raft of Italian and English cars of the 60s. They are a work of art but I could not quite work out how to modify them. The only thing I can think of is to carefully cut and glue the back shells to get the correct dimensions.
Don't be fooled by the curved shape. The centre rivet holds a spring loaded pivot point and the blade becomes flat under load.
Mine are old Italian stock but they are still made.
http://www.tricoproducts.com/Trade/WiperProducts/MoreProducts/Classic