De acordo com as FAQ oficiais, você pode, em teoria, não ter soluções disponível:
Can you use the FDE drives in an external eSATA enclosure and still use the encryption capability? In theory, the answer is yes. Seagate FDE drives and the underlying technology would lend themselves to the type of device envisioned here. However, at this time there are no eSATA solutions available to purchase.
In a related design, Seagate has also manufactured (but no longer manufactures) a line of external drive under the Maxtor brand called "BlackArmor". It uses a Seagate Full Disk Encryption hard drive within a USB enclosure. In addition, it has software to support the Seagate Secure features available in the drive. See here the Maxtor BlackArmor User Guide.
Naturalmente, você sempre pode usar soluções somente de software para atingir a meta "unidade criptografada externa", com o software Whole Disk Encryption, como FileVault2 (incluído no Mac OS), BitLocker (incluído no Windows) ou alguns dos spin-offs TrueCrypt, como < href="https://veracrypt.codeplex.com/releases/view/565079"> VeraCrypt (versão estável disponível) ou CipherShed (ainda no pré-alpha ATOW).