Try going on Air China's US sites. I've bought CA tickets with my c/c online before.

Or you can try Chinese online TA's like
Ctrip: http://english.ctrip.com/
eLong (expedia China branch): http://www.elong.net/

Or call them: 400 619 9999 for ctrip, 4006-171717 foe eLong.

Chinese online TA's are different from major US counterparts in that, you may purchase the tickets over the phone as well, the phone lines are 24/7 and answered all the time, ie no 30+ minutes of holding or talking to machines, and you can also choose to have your eticket itinerary delivered and pay for your ticket in cash only when you get your itinerary.