Greywolf, don't use 700 cm tubes on a 27" wheel. The tube will fold inside the tire causing uneven inflation and unbalancing of your wheel. Keep looking for 27" with prestas.

Post what you need in the "Wanted" part of Bikeforums.com. Go to oldroads.com and post a "wanted" in the classic lightweigts topic threads. Since you are in New Zealand, the shipping might cost you a bit, but a couple of tubes will last you a long time.

Presta valves on 27" are a bit unusual in the USA, but not uncommon elsewhere.

Have you called around to the older established bike shops in New Zeland and maybe Austrialia? Talk to the old timers. Somebody must have what you need.