I'd say the oil seal on the alternator rotor drive may be your problem .
You could clean it up and see if you can confirm it's leaking .
Not a difficult job, but you need a specialty tool to get the rotor free of the crankshaft .
The part under the alternator, is the ignition trigger unit, commonly referred to as ' the bean can ' .
It has an o-ring to seal oil from the camshaft drive for the bean can .
It may be leaking as well, only way to tell is to clean up the area and run the bike a bit and see if you can see which is causing the leak .