I think I'd go for an endcap (just a basic bezel) for the top, with a jump ring soldered to the top and just epoxy into place. For even more subtlety, you could just use a small disc (not too thin or it will look mean) and glue that in place, but it doesn't give you much of a gluing area in terms of hold.
I'd probably give it a little bit of a rounded lip to echo the bands.
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