iTunes gift cards for other countries

I want to buy iTunes card for niece who lives in uk. I can't because I live in Canada and can't fill out my correct billing address. when I go onto the UK iTunes site it allows me to select the card and amount but will not allow me to pay for it with my canadian address. Is there a solution? How can I purchase a uk gift card to send to the uk either by email or mail when I live here in Canada?