For something that size, I'd be tempted to touch it up with something like a chipex touch up kit. If it's 0.5mm then you'll hardly see it anyway.
That said, do you mean 0.5mm or 0.5cm/5mm - you'd be hard pressed to see 0.5mm. Even if it's bigger, I'd still just do the chipex kit (or similair)
Whatever you do - do it fairly quickly as if it's down to the metal, you could get corrosion behind the paint even if you touched it up later.
If you went for a refurb, you never know if it'll be a perfect match etc. - although I know there are some brilliant wheel refurbishers out there that would get it perfect, it's just getting the right one.