I became tired of my life tokens falling all over the place. In addition it is impossible to tell 1 vs 5 tokens apart. Finally when my frustration became great enough this life token was born. The first iteration (magnetless) was nice and helped but was still difficult to stack and would still scatter when knocked over. I then added a magnet and BOOM, awesomeness. Now I have tokens that want to be together, they don't fall apart, they don't tip over, and they don't scatter.
The current design is uses a 1/8"x1/32" Neodymium magnet (approximately 3mm x 1mm).
The magnet hole is designed to be tight enough so that the magnet can be pressed into the plastic rather than glued in place. Based on my printing experiments you may want to size it up or down slightly to get the right fit. Gluing in place with super glue would probably be easier but I didn't want to deal with the mess.
When putting the magnets in the tokens you need to make sure to orient all the magnets in the same direction. The easiest way I found to do this is to take the first magnet and press it into a token. Then using the first token as a guide stack the next token on the bottom of it (so you can see the empty magnet hole). Next drop a magnet into the empty hole and the magnet will automatically orient itself. Once oriented press the magnet into place. Repeat for all the other tokens. To press the magnet into place I used the flat side of a pair of pliers.