A special Marco Pollo Map was sent out to players back in Oct/Nov last year which had codes you could use to redeem one pig per account.
Since those are no longer available (to be mailed) you would have to (hopefully) try to win a contest or code that someone who did get the map has made available. Your best bet on that would be to ask politely either here or on P101 Central if someone has an extra code that they would be willing to part with.