The front seat cushion in the SNOB was in poor shape:
Direct replacements are not available as far as I know, and buying foam for something like this is surprisingly expensive.
Our “good-enough” solution was to get a piece of 1/2″ plywood, paint it to seal it up some, cut out the cushion shape using a jig-saw.
For the cushioning, we cut out and glued two layers of rubber gym-mat/tiles ($12 at Walmart), then covered and stapled with marine vinyl from Jo-Anne Frabrics.
Total cost of new cushion: ~$48