Alibaba is about it for this engine these days. That is straight from the factory, though, so you can order them in whatever color you like, or so they say. Why don't you just run the lights from the battery with the engine you already have? It would certainly be less work. I'm not aware of any other motor like this that has a charging system of any kind.
If I were working with the 49cc motor, and just had to have a charging system, I'd consider trying to wind my own bobbins and find some way of sticking them on there against the flywheel. You'd have to get the regulator first, and experiment with it. You only need 2 of the 3, as the third one is for the cdi you wont have. It can go on in any position, as long as it goes up against the flywheel like shown.
I'd take an open E transformer core and weld it onto the side of the coil's core, and grind it round, and wind on that. But I have this whole thing with transformers going on right now. I harvest the transformers from old microwaves and rewind the secondaries to have more fun with them. I even built my own arc welder. It works really good, too.
