In the past few months, we have covered plenty of Ferrofluid toys here. The CZFerro Spyke Display is another product you can pick up to keep you entertained at work. It comes with a magnetic stylus that lets you move the ferrofluid as you like.
Each set comes with 2ml of ferrofluid. There are also 3 magnets embedded in the base. You can get this for under $70 at this time.