That's exactly what I ended up doing. I found a pet carrier with a bunch of pockets that's also a backpack on Amazon. I decided I'm not bringing anything with me other than a battery, phone, USB powerblock and some cables.
I ordered this for $32
https://www.amazon.com/gp/product/B06XC5FLC7/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1