A mobile case of fabric might be easy to do, I made this last night, took maybe just an hour because I skipped making lining which is recommended.
Make mobile case of fabric
Cut two pieces of the same size, one piece half the size for a pocket and a small piece for the enclosement. Zig zag around all the sides of the pieces.
Fold in the side that is supposed to be the opening of the pocket and stitch.
Pin the three pieces together. Make sure to place the pocket correctly. Stitch together.
Stitch the smallest piece together with inside out, along the longer sides. Turn it right. Pin onto the back of the case and stitch after opening of the case has been folded and stitched.
Stitch on velcro on the inside of the small piece and onto the front of the case. Just measure by closing the case and then stitch it on.