Hardware for Generating Low Frequency Vibrations
What you're looking for is called an audio exciter or a 'bass shaker'.
It's basically the magnet and voice coil of a loudspeaker without the cone and frame. In their intended use of turning walls, doors, ceiling tiles etc into loudspeakers, you connect the armature to a panel, and the mass of the stator is usually sufficient, at audio frequencies, to get reasonable efficiency when shaking the panel.
But they also work right down to 10 Hz, 1 Hz, DC even. The problem at these frequencies is providing a heavy enough stator. The vibration power will divide between the stator and armature in the ratio of their effective masses. If the stator is too light, you'll be shaking the stator more than the load. Choose a type where you can add mass to the body of the exciter, or be able to mount it on something massive.