I made the mistake of asking Mavic head office for spares, they were incredibly unhelpful. But Mavic UK were actually fantastic, even though it was a pretty old wheel. So pretty impressive, but I’d sooner have a normal wheel with normal spares frankly.
(the Enduro is a bit cheeky, Mavic faked up rears for sponsored riders, that look the same as the Enduro you can buy, but are stronger. Doesn’t really inspire, that)
Can I ask, why not a custom build? If you’re worried about durability, it makes a lot more sense IMO, you’re not tied to specific parts and even if you can find the part you need they’re often not cheap.