Hadley's, in Newcastle can order the Cannondale tandems. But at $5k, it's truly cheaper to fly to LA, buy one, and bring it back with you. And you get to have real Mexican food too. If you have way too much cash to spend, try Thylacine cycles.

As far as rarity, I don't think we saw more than 3-4 other tandems in Newcastle. Make sure you get your dealer to stock some extra brake and shifter cables too.