Very nice, but not a motorbike helmet.
The OP needs one that meets one of
these standards:
- British Standard BS 6658:1985 and carry the BSI Kitemark
- UNECE Regulation 22.05
- a European Economic Area member standard offering at least the same safety and protection as BS 6658:1985, and carry a mark equivalent to the BSI Kitemark
If you're after a lightweight one, then go for polycarbonate (=cheap, but OK for low speeds) or carbon fibre (as per soundwave's suggestion but a motorbike-specific one (=expensive and usually full face).
Check the SHARP score before buying, to check the one you pick is reasonably good:
Welcome to SHARP, the Safety Helmet Assessment and Rating Programme, a scheme to help motorcyclists make an informed choice when buying a helmet.
sharp.dft.gov.uk
SHARP isn't perfect, but it's better than guessing.
Try searching for 'dirt bike helmet' or 'motocross helmet' for one with maximum airflow (if you're going to pedal and generate a bit of sweat). That will get you something similar to Soundwave's suggestion.
Sportsbikeshop are good. Ideally visit one of their shops rather than buying 'blind' online. They'll let you try as many as you like until you get something comfy, and that fits:
