This rayshade by Kiddopotamus is fantastic on strollers, car seats, or many other baby gear that you would use outside. It attaches with 4 velcro straps which can stretch to fit most any item. The shade portion has 2 crossbars for support, and is made of a tightly woven fabric which creates a great sun barrier (UPF 50+), as well as repel water. It has a few hidden pockets for your keys or other small items, and can be folded into a small attached pouch for storage (about the size of a diaper).
I like the fact that this shade covers every inch of your baby, rather than just the head and shoulders as most standard strollers. I keep mine folded up in the trunk of my car for those occasions when I might need it, which here in San Diego is often.