What if you hand stitched it to the purse about 1/4 inch inside the seam on the back side, catching the fabric on the face of the purse but not going thru the lining? Like if you fold the edge on the cell phone pocket just a little, the width of the seam allowance, and whipped it down, the stitches could never show. Alternately, what about using decorative buttons or even rivets?