My friend and aerial photographer Mark (YouTube - TheMarkyShow) bought the latest DJI Phantom 4 quadcopter, and it's an amazing thing. He wanted to get the official DJI sun shade but wanted to get flying right from day one, so I made one out of card for him:
Cut out of mount board with a sharp scalpel, duct tape to strengthen the folds, and a couple of Velcro ties stapled on to hold it together. This one fits the iPhone 6+, will probably fit smaller phones, but you may have to vary the location of the cutout for cable connection. If I did it again I might make the side flaps a bit longer, but it seems to work pretty well.
*Disclaimer! I can't guarantee this will work for your controller/phone, it was a custom make for one specific. Template is not necessarily to scale, your mileage may vary. You don't have to go home but you can't stay here. Trousers may go down as well as up. Your home is at risk if you douse it in petrol and chuck a match in the kitchen window.
*EDIT: He's only gone and got himself an iPad Mini to run the 'copter, so it was out with the scalpel for another one. Almost exactly the same, just a bit bigger. Cardboard, duct tape, velcro.