It's not very fun to lug the Apple Watch's included (and fairly lengthy) charger around with you, especially if you don't have any spare USB-A ports or wall outlets. From now on, though, all you'll need is a spare USB-C port. Satechi has released a USB-C Magnetic Charging Dock that will top up the Apple Watch using any powered (you guessed it) USB-C port. You could recharge from a battery bank on a camping trip, a 12V car adapter on the road or even an iPad Pro while you're sipping coffee.
The dock works with all Apple Watches released to date. It can plug in directly, but there's also a short male-to-female cable in the box if space is tight near the USB-C port. The charger is more expensive than Apple's own options (including its native USB-C cables) at $45, but it might be easy to justify the outlay if you'd like a travel charger that occupies very little space and works with many of the devices you already own.