My 3 year old and our dog knocked over his lamp and broke the E26 collar. Rather than ordering online I used it as an opportunity to use the power of community and 3D printing to find a model or find a model to re-purpose for my needs.
I made the test print in PLA with 5mm/s overhangs, and then the final version in PETG.
Outside is ~50mm inside is ~33mm lamp's collar is ~34mm.