Almost every full service restaurant has a sugar-free or a no-sugar-added dessert available. It's usually not advertised, so you have to ask for it. Just ask to speak with the chef, he/she will he happy to discuss it with you. In fact, all the table service menu's now have blurb at the bottom reading something like "we will be happy to discuss any dietary or allergy need with you"
Also, with the rise of low-carb diets, there has been ore of a demand for these types of desserts. Ask around...
Have a great time