simple modular powerbank holder, which can be easily put together
you need only:
powerbank module: https://de.aliexpress.com/item/1005006100282534.html or these https://de.aliexpress.com/item/1005006532624105.html
22 AWG cable to connect plus and minus
Battery clips: https://de.aliexpress.com/item/1005002418222620.html