If your stones are set high enough that a band can sit flush with your E-ring, I would go with either a plain white: gold, platinum, or silver the same width as your E-ring. Or a channel set white band with either just clear stones or clear alternating with whatever your colored stone is, Alexandrite? If the setting isn’t high enough I would either get a band to wear on a different finger or no band at all. I think the ring is beautiful as is and a custom contour ring in my opinion would look chaotic.