I just got my Singer 700 knitting machine out for the 1st time in a few years. I found it has a broken "piece" ... the top cylinder that reads patterns has a broken disk, it doesn't keep the dog locked in place, actually the dog fell out (yes I have it).
There is also Peter in Canada http://www.passapcanada.com/passap/Duomatic.htm, that is the link to his site but I normally call him for parts. It seems to be much faster getting in contact with him. I know that says passap but he also has parts for the studio/silver reed/singer machines. I have bought from him. You might try checking out his parts section of the website or just calling him.