Where can I source extra long headers from

I use a second set of long headers, push them into the ethernet board and then push the protoboad into them.

Digikey has lots of different sizes. Here's a really really long one: SAM1067-50-ND (not exactly cheap though, $18 for 10pcs, with 50 pins each)

_{(source: davr.org)}

No idea on Digikey's policy of shipping to Australia though, but it's quite reasonable pricing for in the USA.

Is this the sort of thing you had in mind or do you need longer ones still? They appear to have other options too, I searched for Headers on the site these were on the second page.