Apple are replacing them for genuine chargers at a low cost.
I believe that this wasnt for third party chargers but faulty Apple chargers
Anyway, You can just buy one of these, They're $29
http://store.apple.com/nz/product/MD836X/A/apple-12w-usb-power-adapter
Im not sure about the US versions because theyre a 1 piece adaptor. The NZ/Aus ones as above are 100-240v and have a plug that can come off (as you can see the split in the picture)
So it might be possible to just use a standard USA to NZ adaptor or just get that