Let me start by saying i am not an electrician.
The cable that powers your monitor is probably, i am still not an electrician, sufficiant to carry a little more current than your monitor needs....
So solder the wires that power your hub transformer to the inside of the monitor where the cable plugs in and fit your hub transformer inside the monitor, i am still not an electritian.
Or use the wire from or rated the same as a four way plug, as that could happily take four appliances.
I have done things likd this myself and am still not electricuted or burnt down, but always best to know your figures, and i am still not an electritian.
Use my advise at your own risk