Does the factory have an alternative ? I heard at one point there would be a nice quilted one similar to the 961 street or the V4. But I have heard nothing since. Why not email the factory :
max.muller@nortonmotorcycles.com and ask if they have something for you. Also there is the possibility of going to a motorcycle seat maker and have them make you a cushion and a cover. You can also go with thicker black foam like you have . There are many possibilities !