Mecha Toad is one of the nine skins released in the multi-part Cap'n Joe's Shop offer. It could be purchased as part of this item deal in mid July 2018.
Mecha Toad could be purchased for $9.99 in a limited time deal that included 16000 coins. It was not available for individual purchase and may not be available for purchase in the future.
Details of this skin may vary depending on location, platform or time.
Note: The part of the Cap'n Joe's Shop offer with the Mecha Toad skin was released again for a limited time in late July 2019. This time the price for Mecha Toad and the 16000 coins was lowered to $4.99.