Seagate 5TB Portable External Hard Drive USB 3.0 Blue = US$124.99 (around NZ$190 delivered) @ Amazon US

Specs:
USB powered - no power supply necessary
Quick file transfer with USB 3.0 connectivity.
Dimensions(L x W x H mm)-114,5 x 76 x 20,35 mm
Compatible with PlayStation 4 (Requires PS4 System Software Update 4.50 or higher)
Works interchangeably on PC and Mac computers—without needing to reformat

Next best price is NZ$289 from PB Tech: https://pricespy.co.nz/product.php?p=3962364

Note: this is not the lowest price I've seen, but it's pretty good for a 5TB portable hard drive already.

Was cheaper previously: https://www.cheapies.nz/node/12737