Paul, check ebay for a TENS unit.
Insurance paid for mine, but they are inexpensive; I have issues at the lower neck (they blame a slipped disk) but the other three slipped disks don't cause pain.
TENS stands for Transcutaneous Electrical Nerve Stimulator - fancy way to say it stimulates the nerve that's causing the problem and you don't feel the pain any more.
Mine came from www.rehabilicare.com, there's a battery box that clips on my belt, wires that connect to soft pads that stick to your back and deliver the stimulation.
Uses three AAA batteries.
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