There are many offers on Amazon and ebay for about 20$ but i wanted to do it on my own.
To get started here are the parts you are going to need:
these powerbanks can be found cheaply on every website (Banggood, Aliexpress, Amazon...) i am just giving one option here. Just make sure it fits the Gopro-Mount (should be a round powerbank)
Step 1: Open and Modify the Powerbank
Next you have to solder one cable to the negative and positive output of the board. The reason i soldered it directly on there (instead of just plugging in a Usb-connector in the front) is because with my setup the Led would stop to luminate after three seconds.
In order to get the cables to the Led i had to drill two holes into the plastic part shown in the second picture.
After that i just pulled the cables through the front and made sure that the charging still works, wich it does :)
Step 2: Installing the Led
In this step we will be installing the led.
I used some glue (nothing specific) to glue the led directly on the aluminium case of the powerbank. Therefore the heat the led produces can be absorbed by the case.
Now the cables of the cell have to be soldered to the led.
To find out wich cable belonges to wich pole of the Led just try out if it lights up before soldering.
Now as you can see i have cut the negative cable in half. That is because otherwise the led will be turned on the whole time.
Step 3: "on/off Switch"
How to solder the parts is shown in the pictures above.
Step 4: Finished Light
The led is very bright so this will be a nice feature for filming at night. Also you can carry the gopro by grabbing the powerbank wich gives it the same use as a handle.
I hope you enjoyed this first project! If there is a project you would like to see in the future or if there are any questions dont hesitate to send me a message :)