12-24mm wide angle: where to buy?

[simpo two]

Having been mightily impressed by a book of New Zealand landscapes, and being headed in that direction in December, has made me think I might need a 12-24mm lens...

So - I can try to find a used one on eBay (for they're a bit pricey new) - but then it dawned on me that I'll be visiting not only NZ but also Seoul, South Korea, on the way.

Out of that lot, where's the best place to get one?

Or maybe I should stay with the 18-70mm and stitch two shots togther?!?!?