How do I mount a second ceiling light from the same junction box
You could use surface mounted box's and raceway.
You would need one box extension on the existing box, this will allow you mount your pendent and then run a raceway, containing the wiring, to a second surface mounted box.
The examples i linked to are all not the same brand, just examples to illustrate what i am talking about. If you go to the home centers electrical dept you will find a section containing these types of products in various brands, sizes and parts to allow you to configure any type of surface mounted raceway/box's.
Of coarse you will need wire, wire nuts, tools and the appropriate knowledge to work with electricity in order to do it safely.