It would not seem prudent whatsoever for someone - especially with no local knowledge (or language ability?) to go to Shenzhen and attempt to bribe anyone, much less government officials, to solve this problem. Guanxi aside, even if you think some local cadres are very 腐败, not a good idea. Cannot emphasize enough how many potential problems could arise from this course of action.

@OP, I would concur with the "lawyer first" strategy. While it may be worthwhile to go to meet with your supplier(s) / contact to try to resolve the issue, the first step you need to take is to better understand your current legal posture and options, lest you find yourself in unpleasant territory once you hit Chinese soil.