Do you have a picture
Our seat tore. We cut a piece of plywood to cover the seat area, covered it with material to match the rattan. Then we made cushions to go on it. Works wonderful.
Do you have a picture?
Do you mean wicker?
A Craft shop should be able to help with all your needs, from book on subject to cane supplies. + a chat about the project too....
We did exactly what Mona did, cut a new seat out of wood to fit over the torn rattan, added a cushion and batting on top, and covered it with fabric. Of course, keep in mind if you have a set you want to match, you'd have to do the same thing to all of them.
Not certain if you mean wicker, rattan or cane but - you can google replacement materials for what you've got and order sections all ready for installation.