I found the advertisement below in a 1938 copy of Riding. I always liked the idea of the child's skeepskin saddle. As far as I know, I don't think there's an equivalent now, though you can buy a sheepskin seat saver. A quick google found the Inkydinky, the basket saddle de nos jours.
In my riding school days in the 1960s and 1970s, one of the ponies had a serge lined saddle, which there was a positive stampede not to clean. Being often away in a dream, I often lost the fight and had to clean it. The serge lining was monstrous: smelly and stained, and I never worked out a good method of doing anything with it other than assaulting it with a dandy brush.