I bought the Revolution for the waterproofing. My first USB charger was an AXA Luxx 70 Plus headlight that also had a USB charger built in. But the waterproofing on that was mostly non-existant. I wanted something better for my tour in Iceland where it rains fairly often.

Some powerbanks work as a pass through cache battery, so do not. On this forum several years ago someone commented that most of the ones designed to work with solar power systems will operate in pass through mode (can be charged and charge a device simultaneously), and he specifically named Voltaic as a brand. I bought their V44 (that model is discontinued) and am quite happy with it. At 44 watt hours of capacity, it has several days of capacity. They make larger and smaller ones. But I am not sure if they are sold where you are. It is big enough that it goes in my handlebar bag.