Look for a GaN (gallium nitride) charger. There's a kickstarter going for one right now that will deliver a total of 100 W through 4 ports, but there are a number of smaller chargers you can buy right now that would be more than adequate for charging bike computers, lights, phones. The Anker powerport is probably a good deal.
If you're buying new gadgets, look for ones that can be charged by USB-C with power delivery (PD). Aside from having a less annoying connector, these can take more power and can therefore charge faster—these are still fairly uncommon, but that will change. And of course, look for a charger with USB-C PD ports.