Part code mate, for Mk5 GTI: 06F903023C although superseded.
There are others that fit (newer ones, part sharing from Skoda/Audi etc), but they can stretch the Mk5 wiring, so I'd just keep with the cheapo one above... for the money it's worth trying. And you can check the pulley when it arrives (it should lock one way and freewheel the other). As it's eBaY / PayPal you've got the payback promise thing, but really, mine's been fine for a few months now, charges well.