Fidget cubes and spinners are ultra-popular now, and cost anywhere from a dollar to twenty. Fidget cubes (center, grey) are covered in buttons, knobs and switches. Fidget spinners (blue, bottom right) are flat and spin on ball bearings like a gyroscope. But a lot of electronics have fidgety features, and you may not even realize it.
Whether or not you appreciate the idea of a smartwatch, the spinning side crown button is perhaps the most addicting and satisfying fidget feature in any current gadget.