we have a shed load of them, loads of cheap ones, even ones from the pound shop ( yes £1 , it'll change the iphone about 40% more )

the cheap ones are good for the girls ( and myself ) to take out and if they get lost, its not the end of the world

We also have a Anker one, this will change 3 phones when out for the full day, ( mainly gets used in disney ( thats disneyworld ) where the phones are used for app's and a camera )

so my advice, a mixture of cheap and the anker