I recommend a separate clip-on book light (or clip-on LED light) that is bright, lightweight, and USB-rechargable.
If the LED is attached to the pen, the weight (of both the battery and light) will be significant and can tire you out for long writing periods. You would also have a better experience for the light to not move too much while writing, which will happen as you move the pen along the paper.
If the LED is attached to the pen, the weight (of both the battery and light) will be significant and can tire you out for long writing periods. You would also have a better experience for the light to not move too much while writing, which will happen as you move the pen along the paper.