The Casio fx-260 Solar scientific calculator is a handy little device. I recently found one on ebay that’s even handier; it has a magnetic strip on its case so you can stick it on a magnetic surface. The ebay description said it was a “30 mil magnet”; not knowing what that was, I had to look it up. Discountmagnets.com‘s page provided a good description of magnetic sheeting and included some prices. Other companies’ websites from the Google search may also be helpful.
Magnetic sheeting seems to be something it could be fun to use and experiment with. You can find it on Amazon, and on ebay.