Hello, my name is George..The carbon filters are available at this link
You do not need to get an extraction kit as the appliance can work in Recirculation Mode
Recirculation will draw the air through the filters to remove grease and other unwanted items from the air that enters it and then send the cleaned air back into the room.
Extraction will do as above but will send the cleaned air out through the tube to the outside of the property.
Kindly be patient whilst awaiting any responses from me as I'm not constantly available.
Please rate the assistance I have given you & feel free to then request further advice if you need to; I will assist as much as I can