Still, I wanted to make photo's underwater. So i looked for waterproof cases, but only found several special cases for the normal s4.
But you can use the Krusell SEaLABox! De 3XL (XXXL) version fits perfectly! The inner dimentions are: 139 x 76 x 16 mm. The height of te S4A is a bit higher 142 mm and the S4A is mostly not mentioned in compatible devices, but it fits perfectly
I tested the seal a box already several times. It had the same IPX7 qualification, but i know for sure I can trust the Krusell!