I know you want something less expensive than the DP seat, but custom seats (as mentioned) will be more since they're customized to your specifics and not mass produced. The DP touring seat is about 1/2 the cost of a custom seat, so...
In the scooter world, Pirate Upholstery
http://pirateupholstery.com/Seat%20Photos%20motorcycle.htm is well known. I had them customize a seat for my Vespa GTS and I absolutely love it. They can add gel inserts for that extra cush, change the angle, or however you want it. If you're looking for something more comfy for a passenger, they can do that, too. But be ready to spend $500 and up depending on the material and labor. Again, I know you're looking for something cheaper, but here's an alternative IF you decide you want something more custom and can save for it. Maybe you can have them add gel padding to the back end and just get a vinyl cover. That should be cheaper. Good luck.
NOTE: If you go this route, you need to ship them your seat and it takes around 2 weeks to make. So, you may be seat-less for a while.