My youngest child and her small hands were having no luck with the other spinners we've printed out, so I designed one to zip tie hex nuts to so that there's just enough there to secure hex nuts on, without adding extra width that could cause problems for small hands.
Any reasonable size hex nut should be able to zip tie onto the body. It should fit a 608 bearing with very little coercion, and the holes for zip ties should be big enough to use without any additional tooling. The goal: keep everything as minimal as possible for fast printing... maybe we'll keep minimizing.

This thing was made with Tinkercad. Edit it online https://www.tinkercad.com/things/lbB7eIwRQHr

MakerBot

Thing-O-Matic

No

No

100

print this at 100% solid infill. There's hardly any fill anyway.