This is simple fidget spinner designed in OnShape and the model is available here 

Its simple to print and uses a 608zz bearing with outer diameter of 22 mm. Use a ceramic bearing that does not have grease. If you have one with grease then you can remove some of the grease with wd40 for it to freely spin.

The bearings are a tight fit and use a mallet and a wooden board to bang it in.

print 2 caps and they should be a decent friction fit. if they come lose then just use some superglue.

enjoy!