This Youtube video https://youtu.be/-7pbjI2wQXY?si=A4dA1IrcY-ImoeZQ shows how to replace the battery pack of LED fairy lights with a USB connector using a custom PCB
www.bigclive.com/USB2LED.zip
While a PCB is great, having a neat case is handy too!
This case slides together and the 4mm through hole can either lock it or be used to mount it.
LED_to_USB_holder.stl | 1.0MB |