How many USB "units" does it need?
USB 2 "unit" is 100mA at 5v; a powered hub should supply 5 units.
The HD/+ use more like 1500mA (which is why most computer USB are so slow if they charge at all -- new USB computer ports have Charge-only modes, which provide more than 500mA when the computer is off).
Pretty much any thing that can charge an HD/+ can charge practically anything else.
Thanks Wulfraed, that's useful information to know.