I also have a Petrol, but it has a lot less structure than an Orca (at least mine, which is basically a soft-sided bag with some padding and I can suspend the recorder a bit).
You can probably find a suitably sized Pelican case, as they come in a million sizes. They are also rather pricey, though. Solid, however, as I think you could run the ones that came with my DPA matched pairs over with a truck with no damage...