You put seats in the Zetec performance section
Any seats from 00-07 will work, you will have to swap the seatbelts(if it's from a different year) and possibly the seat harness itself if they don't match. SVT seats use a different pulg, easy to swap over. Aside from that, you can use lot's of different aftermarket seats with the right adapters. I have heard of somebody installing Contour seats in their Focus with a little modification.