I used a 12V LED light strip, a DC barrel connector, a 12 V power supply and some wires

The power supply and the DC barrel connector I used

https://www.amazon.de/dp/B016LV20X6?ref=ppx_yo2ov_dt_b_product_details&th=1

https://www.amazon.de/dp/B09PD6J4BN?psc=1&ref=ppx_yo2ov_dt_b_product_details

Assembly:

1. Print the Front and the Back part. There are no holes in the model, just add the holes via Bambu Studio. It depends on your light strip or if you want to use a barrel connector. U can also just use a drill.
2. Measure the length of the light strip and then cut it to length.
3. Solder the wires and the barrel connector to the light strip
4. Mount everything into the front part
5. Fore the back part I used normal aluminum foil with some double sided tape to reflect the light. See pictures
6. Close the box

For more details check this light box.

https://makerworld.com/de/models/60268#profileId-62430