If you have have some time on your hands and want an easy, fun project to do, I suggest you take a look at Yuriliku Design's GreenMarker. Granted, you would probably have to be an owner of at least a few books (which may be a stretch considering our tech-heavy lives lately).
All you need is a few sheets of 3M's Post-It Notes, in green of course, and you can whip up a bunch of Yuriliku Design's GreenMarker. Or you can just buy them, there's 25 in each pack.
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