More info would be helpful. There are multiple Bonzini models and neither of mine used a chain to move sideways so I have no idea? I'm guessing it will need to be a small ladder style chain? But it comes in many gauges so you need to know exactly if it fits to a cog with teeth. I needed some for a Mills/Ahrens Stereoscope restoration and was able to figure size from a scrap I had in the spare chain container. I eventually found just enough on US eBay pretty cheap as it's used on a ton of various machinery over there. I have found some in wrecked commercial photocopiers before.