Manufactured home exterior walls
I had good luck getting replacement metal siding from an aluminum fabrication place. It took me weeks to find them but when I did, I discovered they bought pre-painted rolls of flat aluminum and would bend them to match the pattern I needed. They can even bend the edges so the panels interlock.
The color of the new panel will probably not exactly match the weathered panel next to it, and they will not be able to exactly match every pattern, but my experience was this was not especially noticeable.
Replacement siding for hardboard (T-111) can be found in the home improvement stores.
Vinyl siding has become much more popular, especially in the south. It looks nice, the newer plastics last longer and it needs less care and maintenance than other materials.