If the switch has 4 wires it will be two pole - single throw (DPST) where D stands for Dual - meaning two wires come into the switch and two wires go out.
Operating the switch connects and disconnects the wires for on and off.
In the USA two-way means connecting one wire to either of two outputs (SPDT) but in the UK two way means controlling one light from two separate switches.
You need a waterproof DPST switch fitted inside the case and capable of handling the load.
Use Google -select images - enter DPST and see what's available.
Switches may be had from hobby electronics stores like Radio Shack and Maplins.
Under no circumstances should you mess about with externally mounted switches and sticky tape - not if you value your life.
Peccavi
July 2013