Looking for a short story, 40 years old or older: A physicist finds some new law of physics and is told he can't patent it. So he first builds a toy airplane that actually flies without any visible engine, but based on the new law of physics he discovered (anti-gravity), and patents it and makes money. Nobody can explain why the airplane flies, but anyone can copy it following his patent which just says that it works based on some new law of physics.
He makes a second toy: A transparent plastic ball separated into two separate compartments, and inside a small ball which sometimes moves from one compartment to the other (teleportation). A third invention is a gambling machine, where most people lose money, but a small number of people (with hidden ESP talents) can actually predict the outcome and win. All this to convince the government that he should get a patent for his new law of physics.