Nixeus were making a MX518 clone called the "Revel Fit", although with Logitech re-releasing the MX518 I doubt sales of the Fit will be as expected.
Oh ****! I just looked at it. It looks like it could be a cool alternative. Let's see how they both turn out! What a time to be alive.. just 1-2years ago we prayed for this moment, now there isn't only one, but TWO mx518 successors out there!