Site with shopping focus, two countries, mostly the same content except pricing. Best approach?

I'm redeveloping a small website that is new zealand based and up until now has only sold online in new zealand.

Now they wish to sell in australia too. Most site content will be the same, except for contact/locations, product pricing and possibly the odd product detail.

I see a few potential approaches to building the site so it's optimised and not penalized for duplicate content but I wanted to ask for advice from those here, who are much more knowledgeable than myself in this area

The focus primarily is still New Zealand, it's not envisaged that Australia will account for a large share of orders, in the short term anyway but that could change. They already own the .com, .co.nz and .com.au

Possible approaches

1. Redirect both .co.nz and .com.au to .com. Use auto-detect plus a toggle for their country and store that in a session. This means one site for all but it does lose the .co.nz (we are NZ owned and operated) factor.

2. Resolve both .co.nz and .com.au to the same website (codebase) and change content dynamically. Set a canonical link on every page pointing to the .co.nz version. This would presumably avoid duplicate content penalties but also harm AU SEO?


Any advice would be much appreciated in terms of which is bebetter, or if there's another approach entirely.