OK, This used trailer I bought is starting to be quite the project.  Now that we have removed the floor and taken a closer look at the doors, we can now see that urine has created havoc.  Everything looks pretty good as far as the braces are concerned on the frame with the exception of the last one where of course the horses to their duty. It will definately need to be replaced. It is rusted through in some areas and quite weak looking. I don't think that will be a problem. The problem are the doors. They were re-covered at some point with some kind of sheet metal and when we pulled that off, we could see all of the rotted fiberboard. Once that was removed, the doors are in really bad shape and rusted all the way through on the lower parts from urine.

Now for my question. Where can I get replacement doors or what can I do to fix this issue?