Super WalMarts usually carry vanilla and hazelnut in the sugar-free (do watch out... you want the sugar-free syrups). They're in the coffee section.
You may also be able to find them at coffee shops (I can find them at Boston Stoker), or in grocery stores. Sometimes TJ Maxx or Marshalls get them in, back in the housewares section with all the nuts, oils and that stuff.
If you have a Cash 'n Carry around you, I hear they sell them pretty cheap. I've also heard you can find them at World Market.
Torani also makes a sugar-free syrup that can be substituted for DaVinci (Torani used to be made with glycerin, but the new formula doesn't have it anymore.)
You can also contact
www.davincigourmet.com and see if there are any distributors in your area.
If you're going to use them for cooking/baking or general sweetning, you'll probably want vanilla for sure. I like the chocolate, some people don't. I've heard that the Dulce le Leche is WONDERFUL in the Beachgirl's Cheesecake recipe.
I have a Kaluha flavor and Amaretto, but haven't opened them yet.
You can also thicken them up (they're the consistency of a very thin pancake syrup) by adding some xanthan gum and blending well... makes them a great pancake/waffle/whatever syrup.