You can get your Vietnamese Visa in Beijing. It takes about 4-6 days, 350 RMB, and you’ll need to fill out inbound travel information on the form. They don’t seem very responsive to phones so you’d just been advised to go there.
Visa on arrival - Visa at Embassy of Vietnam In Beijing China
Embassy of Vietnam in Beijing – China /High Comission/Consulate For China
Office : Embassy
Street Address : 32 Guanghua Lu, Jianguomenwai
City : Beijing
Phone : 6532 1155, 6532 5415
Fax : 6532 5720
Email : firstname.lastname@example.org
You can also apply online for a Vietnam visa on arrival which seems the cheapest and easiest way to get a visa to Vietnam from China. The total cost is from 35 - 50 USD/person. Click here to see how it works.