I took zheng3's design, printed it at 200% (but only 100% z-axis) and printed one large gear and 3 of the small gears. I then created a 3-pointed backing and some caps to fit on either side of the magnets to hide them.

I printed the gears, used my awesome Bondic pen to glue in the caps on the back of the gears to hold them in place, press fit the magnets (I had a bunch of 1/2"x1/16' neodymium magnets around) press fit and glued (Bondic) the caps to cover the magnets. I sanded all the gears and I am currently waiting for the 3rd coat of Krylon Matte Black spay to dry.

The plan is to do the large center gear in Krylon Antique Brass and the other 3 will be done with gold, silver and copper paint pens and then all will be sealed with a clear coat.

Here is a pic of the unpainted gears clipped to my shirt for testing. You can see the magnets on the three small gears as I had not put the top caps on yet. The backing is under my shirt and has 4 magnets aligned with the 4 gears.