Fidget spinner caps for small 6mm x 1.4mm magnets so they snap together well but can be easily removed. Also a cone shaped divot to help them stay on fingers better.

Magnets I used: http://www.kjmagnetics.com/proddetail.asp?prod=ZD1 Currently on surplus.

Post-Printing

Best to use a drop of super glue otherwise the magnets may pull out.