I bought a keyboard for my iPad Air. It’s the Logitech Keys To Go. Very thin, very light, modestly priced and feels much better to type than it looks (similar in looks to Microsoft’s Surface Pro keyboard), and fits inside my iPad’s neoprene case with ease. James Kendrick has a good review:
The Logitech Keys-To-Go has a layout like most laptops, so keys are exactly where you expect them to be. Spacing between keys is good. The keys you expect to be slightly bigger than the others are just that: the Delete, Return, Shift and CAPS LOCK keys. Unfortunately, there is no indicator LED to show when CAPS LOCK is activated, a minor quibble.
The Cut, Copy, and Paste functions are activated by pressing Fn-X, C, and V, respectively.
The top row has the expected iOS control keys which include Home, Search, and media controls. There is a battery key for checking remaining battery life. I take a lot of screenshots for work so I was pleased to see there is a dedicated key for doing that. There is also a key to take you to the multi-tasking overview, which is very handy.