Apple says that any USB-C power adapter that supports USB Power Delivery of 5W or better is capable of Apple Watch fast charging. You can find these on Amazon from reputable brands such as Anker ...

While the power adapter is compatible with any USB‑C ... Works with iPhone, AirPods, iPad and Apple Watch USB-C wall charger only, charging cable sold separately.

you can use any of Apple’s power adapters (ranging from 18W-96W), or any third-party charger able to deliver over 5W. The Apple Watch cannot charge wirelessly, as it is incompatible with the Qi ...

Apple’s silicon-based power adapters are mostly larger than third ... and an iPhone or Apple Watch at up to 22.5W using the USB-A port. Using all three ports, the first USB-C port can power ...