Depending on your speed and risk, a helmet ranging from bicycle to motorcycle type may be adequate for riding an electric scooter. The following helmets are suitable and are listed in order of increasing protection level:
Bicycle :  for riding below 20mph and riding in a low-risk situation
Downhill : for riding below 20mph but better protection
E-bike / Motorcycle : for riding greater than 20 mph (32 kmh) and in high-risk conditions
Full face : for riding greater than 20 mph (32 kmh) but full protection