You'll have a wonderful crop of grass'' in under a week. Cut a difficult parcel of fabric to size. You might locate these free somewhere, or they're just a few dollars to purchase new. Then there's the extra bonus of locating a treat.
Tutorial: How to Sew Pan Covers for Ferret/Critter Nation Cages / Rat-related comment: Covering the rats' Day Cage during daytime encourages them to be active. Also see aromatherapy with grapefruit scent.
Covered Light Switch & Outlet Plates use fabric or scrapbook paper. apply mod podge to the plate cover, then fabric/paper, the mod podge once more over fabric/paper. When dry, paint around the outer and inner edges and screw tops. mod podge one last fin