Some have found relief from the stock seat with the Stearns ATV cushion, often referred to as the Walmart pad, although they are available at many outlets. At around $18, it's far cheaper than most other options. Reviews are mixed.
http://www.walmart.com/ip/Stearns-Bl...Cover/10727537
Some have found relief from adding a sheepskin cover to the seat. Companies such as Alaska Leather sell sheepskin pads cut to fit dirtbike seats. Deluxe-
http://www.alaskaleatheronline.com/s...-Deluxe/Detail
Rally Special-
http://www.alaskaleatheronline.com/s...e--dsh-/Detail