Which is the best iPad keyboard for a journalist?

Which is the best iPad keyboard for a touch typist?

I’ve looked at a few in shops and need an iPad keyboard so I can use the Apple tablet while I’m on the move.

It doesn’t have to be a full-size keyboard, but big enough for proper typing and preferably with all the main keys in the usual places so I don’t have to unlearn habits.

When I’m on the move I mainly write news, which is usually short snappy stuff, not long pieces. I’d prefer something that doesn’t need separate batteries, but that’s negotiable.