CKPSMS Brand -110V Automatic Bobbin Winder&Thread Stand Fit 1/4"(6mm) Center Hole Bobbins (KP-SBW01 American Plug 110V)

I own four of these. They're wonderful machines. That one appears to be great condition. I would buy a free-standing electric bobbin winder and get on with it until the part showed up on eBay. (Oil it and check the wiring too - the American distributor for Necchi used wiring with poor insulation which oxidized and cracked after a few decades). https://a.co/d/0dLMIXFA