I have never found a fat free one, or low fat. Here is one from a rest. from back East. It calls for sugar, but maybe you can play around with it, and come up with one of your own.

CATALINA DRESSING

1 1/2 cups sugar
1 cup catsup
1/2 cup oil
1/2 cup vinegar
1 T. celery seed
1 t. paprika
1 t. salt
1 grated onion
Juice of 1 1/2 lemons OR 3 Tbsp. lemon juice

Mix all well in blender. Chill before serving.