Are you looking for a power bank or a charger? And what are you looking to charge?

For chargers, the best travel charger is the smallest GaN charger that'll charge your stuff, preferably with a North American / Japanese plug since those are smallest. Throw the appropriate plug adapters for your destination in your bag and you're set. I like my Anker 713 but there are plenty of other options out there depending on what you need to charge.

It's basically impossible to find a charger that's not 100-240V these days, so the only thing you have to worry about is whether the plug fits in the outlet.