I can't remember who, and I haven't found it yet, but one of the ladies on here posted a yogurt based thousand island dressing using yogurt, a bit of mayo (WF I think), sugar free sweet pickle relish, sugar free ketchup, and some seasonings. Maybe you can play around and come up with something that works? If not, these recipes below might point you the right way.
Most Thousand Island dressing has quite a lot of sugar, but this sugar-free and low-carb version is just as good. Feel free to vary the balance to your own taste.
Prep Time: 5 minutes
Total Time: 5 minutes
Yield: 1 cup of dressing
¼ cup mayonnaise
¼ cup sour cream
¼ cup sugar-free ketchup
3 tablespoons sugar-free relish, such as Mt. Olive Brand
1 tablespoon prepared mustard
Mix ingredients together and adjust to taste. Depending on the exact ingredients, you might want to add a little more ketchup or even some sweetener.
Nutritional Information: One tablespoon has half a gram of carbohydrate and 35 calories.
low fat and less than a carb per serving
If worse came to worse, I think the grocery store offers a low carb thousand island that has about 2carb per tbsp maybe you could just use less of it?