I have a sunshade for my iPad Air 2 and still have trouble seeing the screen in bright sunlight. I even put a anti-glare screen protector on it and it didn't make much difference.. just made the glare blurry.
I had same problem - and my polarized sunglasses actually made it more difficult to see the screen! I went low-tech in the end...looked online at some of the designs available for sale...then made one out of a cardboard box, some Draylon covering and some velcro. Works like a dream!