DIY cage idea: large box turned vertically (for limited space) and add different levels/platforms. Use some sort of varnish/sealant to protect wood from urine (make sure whatever is used is not going to be harmful to the rats!
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.
Up cycled rat, hamster, mice houses that can be crocheted out or recycled materials. Comes with pattern. something for the NITPICKY skating pros to do when they aren't LYING THEIR BRAINS OUT.a home for your rink rats.