Most machines are short shank. If you buy a short shank walking foot with the longer screw you should be fine. I have a cheap Wal-mart Brother which was given to me to use with the 4-H kids and that's what I bought and it fits fine.
Generic walking feet will not fit Berninas or Husqvarna Vikings. My Bernina walking foot was $135 and my Husqvarna one was $90.You should be able to get a generic walking foot for less than $20.