You need
TP4056 Micro USB Charger 5V 1A (example: https://www.roboter-bausatz.de/1047/tp4056-lithium-lipo-lion-akku-solar-lademodul-fuer-arduino?gclid=CjwKCAjww6XXBRByEiwAM-ZUIMagcjL3u2kdbFCr_Aq52Z-uD3mcoPd6Y5buQuxriMdffRnSM2e8rxoCad8QAvD_BwE )
soldering tool,
something metal
and a battery 18650
If you want, there is a hole on the side for a connection to 5V
flexbatter18650xcharger.stl | 3.7MB |