You can get a K&N Air Filter for the Honda Forza 300. The K&N replacement air filter for the Honda Forza 300 / NSS300 scooter fits in the stock airbox and is washable and reusable.
The pleated cotton design is claimed to offer better airflow than the standard air filter, resulting in increased throttle response and improved power and torque output. It's pre-oiled and ready for installation.
You can buy the Honda Forza 300 alternative air-filter at the dealer Fast Corner, Bangkok. The K&N Air Filter for the Honda Forza 300 is part number HA-2714.