This is the fancy Singer zig zag attachment. There are (I think) three different cam sets available for different stitch patterns for them. I've seen red, blue and yellow ones anyway.
http://www.ebay.com/itm/Vintage-Sing...AAAOSw9mFWIpoc
Here's the plain one. It doesn't do the decorative stitches.
http://www.ebay.com/itm/VINTAGE-SING...kAAOSwyQtV5KZB
Here's the very collectible (and expensive) Swiss one:
http://www.ebay.com/itm/Swiss-Singer...QAAOSwgQ9VlL4N
Examples are just the first of each type I found, I have no affiliation with the sellers. I've seen the fancy version in action and it does a nice job.
Greist also made them to fit low shank machines.
As long as they're for low shank machines they should fit.
Rodney