You can book directly with the airline .. malaysian airlines, singapore airlines, quantas etc.
Just go to www.kayak.co.in or www.ixigo.com (select international, if you use ixigo) and search there. It'll find fares for you and then redirect you to the airline's website and you can book from there. If you use a travel agent it will actually be a bit more expensive than booking from the airline

Of course a travel agent can also help you with visas. Or the paperwork is straightforward, you can just apply for the visas by yourself, through Immigration NZ's agent TT Services - http://www.ttsnzisvisas.com/