Ahh, permanent fix. Well, I'd normally reserve that one for the dealer. Unless yours is out of warranty.
Let's see, you've got a few options:
1) Get dealer to fix it
2) Wait until next year's Goshen Rally, then get FR to fix it.
3) Mod up a fix for it
4) Fix it using genuine parts
Let's start with #4. First, you'll need to determine what's broken. Is it the cover or the latch? If it's like mine, the cover has a little prong that sticks into a spring loaded receiver on the box. This is what holds it. If the prong is broken, then you can replace the door. If the spring loaded receiver is what's broken, you'll need to replace that. I don't have my trailer here so I can't look to see how much of the assembly needs to be replaced for that.
For option #3, you can get creative. Pretty much any latch you can get at a hardware store will hold the door shut. The least noticeable would probably be the kind that's a steel plate and a magnet, but some people are leery of using magnets near electricity. A simple slide bolt would also work, but that'd be on the outside of the door. A camlock might work, depending on how much room you have to work with. Just head on down to the drawer pull, hinges, etc... section of your local hardware store and see what they've got.
There's no use crying over spilled milk, unless it's on your keyboard.