I modded mine myself.
Got 4 or 5 assorted types of foam offcuts from an upholsterer who works near me. He didn't charge anything and it even included a thin piece of memory foam.
Bought the suede fabric for £17. It's actually Alcantara, the same material used for seats in Ferrari's and Aston Martins, which is why the price was so high for a little off-cut. Shaped the saddle with an angle grinder followed with a palm sander. The stapling isn't done very neatly I'm afraid - one of these days I'll redo it, but I can sit on it for days without any discomfort. Better than my sofa at home:
