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 Portable Fast Charger for Apple Watch
Portable Fast Charger for Apple Watch
Belkin BoostCharge Pro Fast Wireless Charger for Apple Watch +
Belkin BOOST↑CHARGE PRO 3-in-1 Wireless Charging Stand with
Belkin BoostCharge Pro 3-in-1 Wireless Charger with MagSafe 15W
Buy Belkin BoostCharge Pro 2-in-1 Wireless Charging Dock with
Fast Wireless Charger for Apple Watch + Power Bank 10K
Belkin Boost Charge Pro 3-In-1 Wireless Charging Pad For iPhone
Belkin BOOST↑CHARGE™ PRO Portable Fast Charger for Apple Watch
Belkin BoostUp Charge Pro 3-in-1 Wireless Charging Stand w
Belkin BoostCharge Pro MagSafe 3-in-1 Wireless Charger for iPhone
Belkin's new Boost wireless chargers feature turbo charging for
Belkin BoostCharge Pro MagSafe 3-in-1 Wireless Charger for iPhone
Belkin Launches BoostCharge Pro Power Bank With Apple Watch Fast
belkin BPD005 BoostCharge Pro 1 Fast Wireless Charger for Apple