TheThreadThatBinds, that part is called the "hook drive gear". If you search ebay or sewing parts stores online, you'll probably see a few gears that resemble yours, but it's unlikely that they're going to list compatibility for your specific model. You might be better off looking around for a "parts" machine, I have the feeling that a lot of Japanese front-loaders would probably use that same gear, and you might even find it in metal instead of plastic. Also look for a parts number on the part you have left, that might be listed for the ones sold online.