This hard drive from Apricorn has room for 8,000 GB of data. People tend to have very specific needs when buying computer compontents, but this could potentially work well for you.
From Office Monster
Apricorn Aegis Padlock DT 256-Bit AES-XTS Encryption External Hard Drive 8TB ADT3PL256F8000EM
Laserink
Apricorn Aegis Padlock DT 256-Bit AES-XTS Encryption External Hard Drive 8TB ADT3PL256F8000EM