Explain your situation on a white paper why you are unable to provide an official letter from your employer. Sign the letter. Attach some sort of copies like pay cheques, signature from coworkers, benefit probes etc.
I have experience certificate of that organization and as well appointment letter but it can not be verified from the mentioned telephone no’s which are on experience certificate.
But my manager is in my contact can I take reference letter from him which mention that organization closed his operation.