Mechatron is one of the three skins released under the Ancient Knight part of the Mechanos offer. It was available for purchase in late June 2017.
Mechatron could only be purchased for $19.99 in a deal that included the Supremus skin and either 50000 coins (Browser) or 1800 DNA (Mobile). It was not available for individual purchase and may not be available for purchase in the future.
Details of this offer may vary depending on location and platform.