Since nothing more had been heard from the guy in the US about exporting the partitions over here, I decided to have a go at making one myself. I have attached some pictures to show the results. I started with an old piece of cardboard to get a rough template, then cut the shape from 15mm MDF. Finally I persuaded my better half to help me cover it with black material before fitting in place. I followed the instructions from the US site to get the positioning right. I think it looks ok, and it definitely reduces road noise.
Jim