Do you have the model with the removable seat?
I think they went away from that about 5 or 6 years ago, give or take. The newer models have a pretty nice seat that is permanently mounted (I have a 2013 model).
If your seat is indeed removable, I would recommend the comfy manta from ACK:http://www.austinkayak.com/products/146/Comfy-Manta-Kayak-Seat.html
I used that seat on an Ocean Kayak Scrambler for a few years, and I really liked it. High seat back and really comfortable.