Is your machine a low shank? I think most Vikings are. If so, you might be able to get away with a generic. If your's takes snap on feet, you might have to unscrew the ankle and screw the foot on by itself. Some quilt shops sell them. Do you have anything local? Or a Sewing/Vacuum store in your town? I can get any part I need from my local sewing shop. If he doesn't have what I want, he orders it.
You could try ebay too.