nb if you buy a 30+ gig pod it will come with a mains charger... this will be a us plug... best thing to do is go to your local apple store and just buy a plug for it (no wiring needed, it just plugs into the bottom of a cord).
If you are buying it online, rather than going to the usa, it may be worth sending it to a friend in the usa and getting them to post it. No tax issues there.
If you are buying a Nano then the usb lead which connects the pod to the computer charges it and as all usb leads are universal... no conversion problems at all.