Thank you Pessa and Gavin for replying. Actually, we are ready to pay anything just to get this document. His visit was approx 8 months in Xiamen,China that too on Business visa, type F. We contacted a couple of online websites in this regard and they declined as soon as they hear it's Xiamen. Also in Xiamen they require your fingerprints in order to get PCC.
LOE is risky bet but only option left for me at the moment. I read a similar thread where the person was in same scenario, he wrote a LOE and attach all correspondence with visa companies etc. HIs PCC was vaived off, Fortunately.
Really don't know what to do here