Hello.
I'm afraid there is no known easy way to get a visa for a parent. (I can only remember hearing of one special dispensation in recent years, and that was when the only family of a lady of 103 were in NZ, and her UK care home was closing down, so you can see it was in EXTREMELY unusual circumstances.) You have presumably found the Immigration NZ web pages about this issue, here
http://www.immigration.govt.nz/migra...nt/default.htm. That's the route for sponsoring a parent.
Is there any other visa your mother might be eligible for? Is she still of working age? Does she have skilled qualifications?
Otherwise, are you aware that she'd have the right to spend half her time in NZ as a visitor?