I do exactly what you are looking for.
I use an external Port Replicator to achieve that goal.
It connects to the USB 3.0 connection and provides 2 HDMI outs, Network and 5 additional USB ports.
It has its own power supply and does not draw power from the laptop.
Currently I am using the Dell 3.0 4K Port Replicator - but I am sure there are others out there.