Model originally uploaded to Thingiverse at https://www.thingiverse.com/thing:4912102.

The original didn't quite fit my boy's cage, so I first tried scaling up for the next gap but then it was too fat to fit through. I could probably get away with scaling down but at this point decided it was time for a do over (which ended up being required as the base of the cage shifted once it was lifted off the table).

As a Customizer, you will have more control over various dimensions. I have also rounded off the bottom edge a bit more for comfort. Also added a self supporting version for more variety of cage types.