[NiceCrocs]

I give mine torn up toilet paper (if you can get charmin, I find it's not very dusty) but she also stuffs her nest with her normal substrate (Kaytee clean n' cozy) so you can just let them do that if you like.

I've also seen people (mostly ones who do natural- style cages) offer Timothy or alfalfa hay as nesting material, so that may be an option if you're still reluctant to use toilet paper