I’ve been investigating this personally as mine’s got a bearing issue on it and in my opinion it makes more sense to get a new unit from the States.
The factory unit is made by Valeo and they are on special at ecstuning at the moment for usd$189. Shipping is expensive from ecs however ($130+) but in reality true shipping cost should be about us$89 with usps standard express box. - if you use someone else with an account with the likes of ups ect it’ll be cheaper again still, I actually think if you pack it tightly it might be cheaper still or if you ocean it with kiwishipping.
There is a catch however, through my investigation Valeo makes 3 tiers of this unit and it seems one is a remanufacture, one is OE (ie BMW) and one is Valeo branded. Without seeing all the units side by side it is very hard to judge if they are exactly the same.
My opinion however is alternators are not complicated units and they are all much the sameness really - so any good branded replacement will be just as good as the original unit - ie anything from Bosch, Valeo, Lucas or Denso is a good alternative if you can find them cheap and only slightly more expensive than a rebuild (which probably uses Made in China internals)