You can use Singer grease (which can be mail ordered from places like Sew-Classic and Jo-Ann Fabric) or Vaseline. You could also use something called Tri-Flow Grease which they sell at bicycle shops, if you have one near you, but I'm guessing the Vaseline will be the easiest to get.
- Rain
Vintage Singer Sewing Machine Blog
http://vssmb.blogspot.com/