Hey CHA
I'm in South America trying to get home by freighter too...only I'm trying to get to Canada!
So, I'll share with you what I know...
Oldendorff is the best option...and especially for you - they have freighters from S. America to New Zealand (if I remember right). Check their website...
www.oldendorff.com. The lady to email is Renate Renaska (use the contact us button on their site)..she's super nice and will probably find you something...but...this will cost you about 50 bucks US a day....which is pretty expensive in my books....but that's the best bet.
Also...I've heard Valpairaso is the best port to leave from in S.America...lots of grapes being shipped out of there and harvest is coming up soon...so I've been told...so wines and grapes will be being shipped out real soon...so your in thr right place apparently.
Oh...the cheapest option I think is by tramp vessels...which are freighters that stop in ports at short notice - like taxis of the ocean. You can check this site:
http://Freighter World Cruises/places/short.html for updated schedules.
Now...let me ask you for some help in return....
We're (me and my girlfriend) trying to get as close to home as possible from Patagonia...but we'll probably have to bus it up to Santiago/Valpairaso or Buenos Aires to find a ship home. IF YOU FIND ANYTHING OUT PLEASE LET ME KNOW...cause maybe it will be usefull info. for us too.
K, that's about all I know...hope it helps...and good luck...finding freighters seems to be pretty difficult (freighters that aren't cruises, that is...i.e., no swimming pools, saunas or 100 US/day costs!)...we're gonna resort to walking up docks and asking boat captains we think...if that's even possible...
Ciao,
Jeremy Sager