The days of getting hold of newspapers by the truck full are sadly gone .Used to use shredded newspaper for bedding and whole sheets under bowls etc .Roll the lot up and burn .Don’t use straw as the pups will eat it resulting in vet bills and possible dead pups and that’s from experience .Like Sean said rags ,towels old bedding anything washable .
Large pet beds are reasonable now ,buying a few could rotate them .I guess dependant on external heat source .