Asian nations get most of their weapons from the European Union, Russia, and the US. China sells weapons, too, but not as much as the EU, Russia, and US. This is true for most nations in the whole world.
I think China works with other nations and spies on other nations to secretly obtain weapons technology from the EU, Russia, and the US to complement China's indigenous stuff. China even secretly works with and spies on Americans (I hate stating the obvious, I got to here).
I would not be surprised if China has secretly worked with South Korea, Japan, Taiwan, Philippines, Australia, Saudi Arabia, India, Israel, many other US allies, and the US itself to obtain US technology. In fact, a few information leaked here and there reveal this is all true.
So China does "buy" weapons from Asian nations and many other nations around the world.