It's doubtful that Seagate will provide you a replacement enclosure for the drive....BUT! You can purchase enclosures at a local computer store such as Best Buy or some place like that and still use the drive externally. 
To all users: If your data is stored ONLY on an external hard drive, then it is NOT a backup. A BACKUP is having the data stored in TWO or MORE locations. If it is only in ONE location, you don't have a backup at all. If the data is important to you, then have it stored in multiple locations to prevent data loss.
