Nerve biopsy test: Is it done by a neurologist or rheumatologist?

What kind of doctor do I see for the nerve biopsy test? My PCP sent me to a rheumatologist for a diagnosis. She feels it is fibromyalgia but prior doctor in Wash. state said it is neuropathy. She won't arrange for the biopsy. Which kind of doctor can finally give me a diagnosis or is she right? All she is offering is amitriptyline for pain. I do take norco too, but my PCP would like me to get off that. I need advice.