The simple answer R. McGuinness suggests to finding a Doctor who will euthanase you on your request is not realistic.
You would not find a GP in consultation who would openly say they would do it for you. You can make an Advance Directive in your Will of your wishes in relation to this matter while you are of sound mind and capable of careful consideration, should you become so severely incapacitated that you are unable to communicate mentally and physically.
As the law stands, ,the opinion of two independent physicians is required to determine that your condition is irreversible before any life support treatment is withdrawn. This does not mean that you would be given a drug to gently put you to sleep permanently to end it all but in the event of a life threatening condition that no treatment be given to maintain or prolong life.

Robyn Wallace, Mount Maunganui.