Do you know how old the remaining swan is and how the other swan died? The worst case scenario would be that you go get another swan only to have the remaining swan die from old age or both swans die from the same cause as the first if it was not old age. Another concern would be that the remaining swan does not accept the new swan. Whooper swans have a 6% divorce rate, so there are no guarantees that he/she will accept another swan.

You would need to find a swan of the opposite sex so that fighting can be somewhat mitigated. Usually, not always, but usually, male/female associations do not facilitate aggressive territorial behavior as a male/male or female/female association would have if the swans of the same sex are not raised from a very young age. Even then, again no guarantees!

You might try Sylvan Heights Waterfowl in North Carolina or possibly Knox Swans in Indiana, although we're really not sure if Knox carries this species. We did purchase 2 Whoopers from Sylvan Heights and they are great birds. The Regal Swan