I got hold of a spare seat for not a lot of money and then had it re shaped and covered by a guy in Harrogate who's name escapes me at the moment.Google him, old boy well respected.
£100 for the whole re shaping !
wider and 1 inch thicker for rider to spread the load more.
Wider , thicker and the seating angle tipped forward for the wife.A huge improvement, apparently, for the pillion.
Much better than the american offerings which sell for a lot of money and are not good at all.