How easy or difficult it is to get a PwD certificate? I have called few hospitals listed in the NTA NEET brochure but not much positive response.

You haven't mentioned the type of Disability you possess. Now if it is a locomotor disability, it i allowed upto 70% and for audio and visual disabilities, upto 40% is allowed. Beyond this range, you will not be eligible for PWD reservation but still can appear for NEET if you fulfil the eligibility criteria and also take admission in Medical College. PWD is not a vertical reservation. It is a horizontal reservation within your Category. And you should have a disability certificate from any Government hospital for claiming PWD reservation. But before appearing for Counselling, if you qualify in NEET, you should visit any of the Disability assessment centres listed in NTA NEET Information Brochure. The medical team will conduct few tests and then give you a Disability certificate which is mandatory for claiming PWD reservation in NEET Counselling. Without this certificate you might not be able to claim PWD reservation inspite of having a Disability certificate. Now this is the process. If the protocol is followed diligently and you fulfil the parameters, you should be able to get the PWD certificate easily.