Here is a somewhat easy custom to do, puting magnets in a Microman or Micronaut figure. I purchased a collection of "Rare Earth" (Neodymium) magnets from Ebay. I searched around for something small that would work.

I measured the magnets against the feet first then I took a small drill and drilled opening for the magnet. Be very careful not to go all the way through the foot. I then took an xacto knife and cleaned out the hole, and in some cases trimmed some extra material out of the hole for the magnet. I tested my magnets first to see if they would fit in the completed hole.

Finally, I then placed a drop of superglue on each foot and inserted the magnets. I let the glue dry for a day, then my Microman was ready to use.

This is my one of my Micro Doc customs with the magnets drying in his feet.

Magnets come in various shapes, sizes and strengths. Some of the small magnets are more powerful then you may think. Be careful with any strong magnet as it can cause you to get skin pinched when two very powerful magnets come together