My guineapigs love the thick wooden structures from pets at home that you can make into ramps or bend into caves, they can hide in them and they love chewing them, if you make them low enough they can climb on them too., they were on offer for £4,99 recently but I think they are usually nearly £6.00 near me, they also let the air through when its warm. Also the thick cardboard tubes they're not expensive either. You could try hay balls hung around that they can lean to eat. Mine don't seem to bother with chew toys although yours might, hope that helps. Silly xx.