You need to click the link below for GT Covers in Colorado for seat covers for you Prius with seat air bags. They make covers that fit great and look like the original fabric. They offer three fabrics, one is water proof, if that is a concern to you. You can install them yourself, however the rear seat can be hard to get out, so allow extra time, or get help. Look at the website where you can see fabrics and order direct. A full set, front and rear, will cost about $275, which I think is a great deal after having mine for 9 months, they still look and fit terrific.
http://www.greatcovers.net/