How to convert Gilera runner 50 to twin headlight?

I have a Gilera runner 50 with the single head light (which is not bright enough for dark roads). I have bought a twin head light unit and would like to wire it in. I were going to wire the original switch to the normal beam and add a toggle switch to the removable panel on the bars for the high beam. Does anyone know what voltage/amps a toggle switch should be able to take to run the high beam on this scooter? Are there any wiring kits available for this sort of thing? Are there any other ways of doing this?

I tried doing above, but it didn't work. What I did is took the live from the original switch into a on/on toggle switch then one wire to each the normal beam and the high beam. Theory being that I could switch the lights on with the original switch then switch high and low with the new toggle switch. Didn't work only one side of the toggle switch worked. I buzzed the toggle switch out with a multimetre and the switch is working fine. Why isn't it working do I need to do it a different way?