What are some good guinea pig toys?

In have 2 little guinea pigs, Oliver and Sampson, and I would like some good toys that are cheap or can be made from household items. Oliver and sampson are currently in a 2x4 c&c cage. I would like touys that dont junk up a cage. Oliver and Sampson have- hay hammock, 2 food bowls, 2 water bottles, a pigloo on a comfy bed, a snuggle sack, and a herb 'n hay tunnel. They get lap time and floor time each day. they get 3 small bowls of veggies each day. I feel they are happy but, I would just like to make them as happy as posible. Thanks for the help and please post any health concerns but, I do feel the cage is safe. Thanks so so so so so much. I have already looked at the amazing website Guinea pig Cages so all of those ideas I already know. =)