Thin Household Cardboard for Eight Rescue Gerbils (Parkdale WV1)

Hi there! I am looking for clean, thin household cardboard to use as chewing and boredom-relief material for my eight rescue gerbils. It makes a huge difference to their mental health as they need a lot of stimulation/enrichment. I am looking for items such as empty cereal boxes, toilet roll tubes, kitchen towel rolls, egg cartons, chocolate boxes, biscuit boxes (eg Ritz) etc. I don't require cardboard with lots of plastic or tape over it or with a strong chemically smell to it or cardboard that is corrugated. Thanks