You need an extra long case. I've owned two Originals, one came with it's own flight case which judging by the stickers on it had actually been on some flights, and for the other I was able to source a suitable hard case from my local musical instrument shop amongst their stock of spare used cases in the days when they used to have such things. Both cases were the same internal size (within a few mm) so it would appear that it is a standard, albeit one that isn't very common. Unfortunately I don't have either bass any more so I can't measure them for you.
Alternatively you could ask Overwater. IIRC they still make basses with the Original shape as a custom order so they should know of a source of suitable cases.