Look for Drum thrones. No wheels, Backrest or the Motorcycle type.
It's then anything that feels comfortable for you and you feel you can sit on for at least one hour. I would stay away from anything under $75 as it will end up breaking, or any of the simple hole and pin height adjustment.Look underneath the cushion and make sure the support bracket arrangement extends as much as possible across the circumference of the cushion.
Also consider the weight. The high end Roc n Soc hydraulic tend to be quite heavy.
Go to your local Guitar center or music shop, sit around and see what tickles your fancy
http://www.guitarcenter.com/Search/Defa ... rc=thrones