On the early x250's the spare carrier fitted under the rear of the van and the winder was accessed through a hole covered by the rear door, these were very unreliable and used to seize and some failed with the loss of the wheel. The carrier was later modified and the winder accessed behind the rear wheel, there was a recall for this.
The new style carrier is often for sale on e-bay but you must get the right one for your van, either 15" or 16" as they are not interchangeable, also to fit the carrier requires fitting rivnuts to secure of the winder.
Mike