Get it from your district exit entry bureau office, if you are not in China you can send someone on behalf of you with your authority letter and with complete passport copies, sample authority letter given below;

From: Mr. xyz

Passport No. xxx, Contact: 12121212

 To,

Entry Exit Bureau xxxx (Address)

Date: 00 May, 0000

Subject: Authorization Letter to Collect Police Clearance report on my behalf

Dear Sir.

I, xxx, hereby authorize, xxxx, passport No xxx to collect Police Clearance report on my behalf. She will also claim my check and other land related documents from your office on my behalf. I am also sending my old passport photocopies to show the details of entry and exit stamps.

You can reach me on my phone 121212 in case any further clarifications needed.

Thank you very much.

Xxxxx