There is a fellow in Hayward CA who has a bunch of parts for older (mid-70s) Lamborghini tractors like my C603. These older parts are harder to find on the web. He is very knowledgeable and very professional with his business. I have bought many parts from him and never had any problems, including steering clutch, hubs, bearings, knobs, headlights etc.
His name is Bill Stafford, of Stafford Equipment
Phone 510-537-3332