This hard drive from G-Technology has room for 5 TB of data. The form factor is 2.5".
From OnBuy
SanDisk Professional 5TB G-DRIVE ArmorATD, Dust, Drop, Shock and Water resistant, portable rugged external HDD for MAC, Up to...
Clove Technology
SanDisk G-DRIVE ArmorATD External HDD 5000 GB Black