I purchased the air from a co-worker who used it with a iPad mini. He lost the original cable and slider. I can purchase the cable but the slider is not available for purchase according to DJI. Which makes no sense.
I believe he is referring to the rectangular shaped plastic which keeps the phone side of the cable attached to the swing arm of the RC that slides up and down depending where your phone sits.
What do you need that slider for? For me it's so much better to not use one. It's more difficult to get your mobile phone connected on the RC with that slider than without it.