Here's a cool idea I've thought up. It might be easier if you had glassing skills yourself, but if you don't you can find someone who does to do it for you.
Get your board, and cover the whole thing in like a camping mat, the kind that's about a centemeter thick and rippled , and then cut out the outline of your board out of that. Get some ten minute epoxy, and epoxy the next layer on, some inch thick styrafoam (get the lightest stuff you can find, it absorbs most impact) and do the same thing. Then get some packing tape and make the whole thing secure.
Next, this is where the glassing skills are needed, get some ten ounce cloth or mat, and glass with epoxy (two layers with the cloth) each side. Cloth is easier, because you can lap the rails, and it keeps the whole thing together better, but mat is usally cheaper and still works.
Now, you can either take it where your traveling to, ship it to someone else, or finish it. To finish it, you need to get a small grinder bit for a drill, and cut out a quarter inch wide area of glass down to the foam all the way around. Don't try and take it off the foam, just leave it. Get a hacksaw blade, CAREFULLY cut through the foam down to your board, this is the part where if you screw it up it's not very board healthy, but if you do right you get your case out of it. After you get your surfboard back out, or are able to, get it back in and put both halves together. Get a good piano hinge ,and mark out where the screws need to go. When that's done, drill holes adn fill them full of more ten minute epoxy, so the screws have something to anchor in.
Get some snap hinges, and do the same thing, or epoxy them on. If you do though, sand the area so the epoxy has something to stick to, and you should have a custom board case!
You can even customize it, by spraying designs onto the foam before it gets glassed, and if you wanted could put a logo on it (rusty could make a rusty case).
If it gets a good glass job, these cases can last a while, take abuse, and still can be cheaper, and if you get good, maybe could market them!