The Belkin BoostCharge Pro Fast Wireless Charger for Apple Watch + Power Bank 10K is a capable battery pack, but it's not cheap.
Belkin BOOST↑CHARGE™ PRO 3-in-1 Wireless Charging Pad with
Belkin's new Boost wireless chargers feature turbo charging for
Belkin Wireless Charger Apple Watch Power Bank 10K
Belkin Boostcharge Pro Portable Wireless Fast Charger For Apple
Belkin launches new BoostCharge Pro 2-in-1 MagSafe & Apple Watch
Buy Belkin BoostCharge Pro 2-in-1 Wireless Charging Dock with
Belkin BOOST↑CHARGE™ PRO Portable Fast Charger for Apple Watch
Belkin BOOST↑CHARGE™ PRO Portable Fast Charger for Apple Watch
Belkin BoostCharge Pro Fast Wireless Charger for Apple Watch +
Belkin BOOST↑CHARGE™ PRO Portable Fast Charger for Apple Watch
Belkin BoostCharge Pro 3-in-1 Wireless Charger with MagSafe 15W
Belkin BOOST↑CHARGE™ PRO 3-in-1 Wireless Charging Pad with
Belkin BoostCharge PRO 3-in-1 Wireless Charger with MagSafe for
Belkin BOOST↑CHARGE™ PRO 2-in-1 Wireless Charging Dock with