I needed a shallow light fixture base for a solar project for the kids' school. This will fit the Leviton "Keyless Plastic Ceiling Lampholder" model R50-08829-CW4.
This thing was made with Tinkercad. Edit it online https://www.tinkercad.com/things/2UatK5RmU49
I design and print stuff for my kids. I hope yours will enjoy them too!