Thanks.
It looks as though it's powered from the USB hub, in which case it
would be 5 Volts DC, if trying to power one separately the 5V supply
must be stabilized, about 0.5Amps would be more than adequate, it's the
hub what determines the amount of current drawn the power unit has to be
able to provide it.
Be careful of unregulated 'wall warts' many aren't regulated and the
voltage could easily be around 7 Volts or so.
Davy
It would be a 5V regulated (switching type) PSU, though the
current capability of the original doesn't need to be
matched exactly. What I mean is, USB spec allows up to
500mA per port, so in theory it is possible to use upwards
of 3.5A and you could aim for and buy that if it's
reasonably priced, but unless you plan on having all the
ports populated simultaneously with high current
peripherals, you could probably make due with a 2A, and a
different brand 7 port hub I have here has a 3A PSU.
Other issue is the size of the connector it needs,
presumably a typical DC barrel connector in 5.5mm OD or
smaller size, and variable possiblity for ID, inner
diameter. Considering it has 7 ports, I would guess it more
likely to be 5.5mm OD and 2.5mm ID.