Hi Filipu. I've done several of these and have the required tools, including a Dremel to make the hole in the headlight's plastic shroud. If you are just going to use minimal load items with the outlet (e.g., GPS, cell phone sharging, etc) and not things like an actual cigarette lighter (heavy load), it is usually wiser to tap into the wiring harness behind your headlight. It is easy to tap into an appropriate circuit that is "live" only when the ignition is on. In fact, depending on how your bike is wired, you may be able to tap into a circuit that is "live" only when the engine is running. It depends on what you are using the outlet for - that will determine whether you need to go back to the battery.
By the way, there is a great electronics market (actually several) between the Xisi and Ping An stations on Line 4 (West side of the street). You can buy anything and everything, including reproduction harnesses and connectors for vintage motorcycles. I have an old Indian motorcycle and took a sample of an ancient connector to a shop who, amazingly, found an exact copy. They also have marine grade USB connectors for flush mounting, which might be more appropriate for you if you just need a powered USB connection.
The fellow on motorfans used an inline barrel fuse in his connection (you can see it [black tube] on the red wire above the battery).
Give me a couple of weeks to finish the remodel on my shop, and I'll set you up, gratis, and show you a few tricks about installing these things. We need 220 power for the dremel. Be impossible for me to describe it online. I'm a really shitty photographer.
