This information from Busch + Müller works on batteries and has an on and off button. The front light can be pushed, waterproof and comes with holder.
Dimension of front light: 5 x 5 x 10 cm (L x W x D)
Size holder: 6 x 2 cm (L x B)
Type of lighting: led
Number of lux: 80
Clamp diameter: 22.2 to 31.8 mm
The headlamp is rechargeable.
Suitable for steering attachment.