I would start by creating a boundary surface between the elipse and the edge, assuming the sides of the button should be straight.
Then the top of the button, and there are different shapes you might use with the top, some easy, some not. But generally, for non-planar top surfaces, you might consider placing a plane at the top or bottom of the button face, depending on if its convex or concave, placing a point at the high or low point of the center of the button face. Then use a Fill surface using the elipse, with the point as a control curve.
There are other ways that would also work, but that's the one I'd try first.
Hey Matt thanks for the reply. Your suggestion worked out pretty well. Finally was able to create the button.. Kudos..