The recommended power adaptor for the SPD::ONE KICK pad is the BOSS PSA series.
They can be purchased at any Roland/BOSS dealer.
NOTE: The current draw of the SPD::ONE KICK is 300 mA. Please use the PSA-S or PSA-S2 (with a maximum output current of 500 mA). Please refer to the related article: BOSS PSA adaptor: Specification Differences by Model
CAUTION: The use of any other power adapter may cause malfunction and/or permanent damage to the product.