You don't need an eSATA port, in fact that's the last thing you want as the interface isn't very resilient to any interruption. Stick with USB, it's faster anyway!
In terms of what to go for:
3.5" external enclosure -
Link
Toshiba X300 4TB -
Link
Doing it this way, you're just using a standard 3.5" which can easily be upgraded/changed if needed - and it's significantly cheaper!