Any recommendations? I'm looking for something very light weight but also durable. also something that is small enough to fit in the tank bag
Think big or stay home. Rig up your trailer and do what this guy did. Disappear to Brazil before they catch you.Size is the limiting factor here. I take a few small chargers with me and as they get used up I switch to the next one.
A decent option could be the same, but as they run down connector them to a USB running off the bike to recharge while a second one is being used.
Solar panels are great, but very limited in their output for smaller sizes.