The Honda S2000 can suffer with rust in the lower rear wheel arch, and these panels rust through. They also carry the edge for the rear quarter panel to attach/butt up to.
From today (12/05/2022) you can order these very much in demand parts from Ex-pressed Steel Panels. In the picture below you can see the OEM item in black in the background, and the Ex-pressed Steel Panel in the foreground. They cost £111 + VAT per panel.
There is a 30 day lead time on any orders, but from today you can place orders HERE.