What I did is printed out the logo on photo paper, carefully cut it out, and superglue it to your card. Works like a charm to get cashiers to at least try it. And has proven to be more durable and authentic looking than you would think.

however, as people in this thread have stated, it is becoming harder and harder to use Discover in China. More local unionpay terminals are simply not compatible with Discover Card. And the new chip on the Discover card almost never works, even when only swiping at the terminal does. Very frustrating.