Dear Sir, I am from Mongolia. We don't have an embassy of Brunei in our country. How do I get visa?

Dear Sir, Does the embassy in Beijing has jurisdictions over citizens of Mongolia? I am from Mongolia and would like to visit a friend working there. But we don't have an embassy in the country. Is there any possibility if it on arrival at the airport for Mongolian citizens /please understand it is costly to travel to Beijing only for application?