Sorry, that's a poor excuse. It doesn't take a great deal of forethought to appreciate that shock absorbers are likely to need replacing at some point, and to ensure that there are at least some available off the shelf in the UK, even for a relatively 'exclusive' model like the Trekking. I'd be sympathetic if they were struggling to get hold of some esoteric part that isn't a routine wear-and-tear item, but shockers don't fall into that category.
Oh, and this is 2018. You can get stuff couriered from just about anywhere on Earth in just a few days. It should be possible to get parts to the UK from Italy in 48 hours, max. Anything longer than that and they just aren't trying hard enough.