There can be many different cams for each brand of machine. Most do not interchange between models. I think Singer has 4. (I have three Singer types.) I've seen photos of 8 different Kenmore cams. Some are easy to find, some are not. I don't know about the other brands, but don't assume that just because it's a "X" brand cam, it will fit your machine. I almost bought a Necchi at a garage sale that took cams. It would probably take forever to find those cams.
It's much easier to get one with the cams already there. There is a White (Gritzner made) on Craigslist in my home town with all the cams, accessories and manual (+nice cabinet) for $100.00. Look for one like that. That fairly well assures it's not too far from it's original owner (at least in my mind).
http://dallas.craigslist.org/dal/hsh/5743498526.html
bkay
bkay