Simple pulling mechanism cannibalized from a cheap consumer product?

Hi, apologies, I’m not an engineer but hoping you all will have suggestions: for part of a film set, I need to have the look of several plastic (lightweight) chains swaying as if from light wind, as they hang vertically. But we can’t have actual wind due to fabric elements as part of the set design that can’t move, and audio. It needs to be done autonomously.

Here’s what I’m thinking so far. I’m hoping to find an inexpensive product I can cannibalize for this mechanism. I was thinking an oscillating fan, but maybe there’s something easier (I’d have to dismantle the fan because of noise and actual wind)…

I’m going to have several plastic chains hanging from a 10 ft small pine plank, in an array / spread along it. The plank will be hanging about 2 ft from the ceiling. I’d like to have a string attached to one end of the plank going horizontal, then through a plumbing 90 degree elbow (lubricated inside), so the string can run vertically down.

I’d like to have the string attached to some cheap item/motor that will slowly pull back and forth on the string an effective range of 3-4 inches.

Any ideas on what product to use/cannibalize for this pulling movement?

TIA for any ideas.