Have you call around & check for flight options from some of the Chinese travel agencies or tour operators based in Greater DC metro area, Phila or even NYC area - as they can tell you what routes are still available & best e-Ticket prices (not sure if you will find any last minute fare deals) on carriers like Air China, China Eastern, etc.

The ones in NYC are open even on Sundays & you should be able to reach them via toll-free #'s to check their inventories. Good luck!