And here is a question asked and answered about subsituting here on Food51 about a year ago http://www.food52.com/foodpickle/1531-is-there-a-way-to-substitute-pomegranate-molasses-with-something-or-a-mixture-of-somethings-from-my

If you can find the juice, make your own! Here's a recipe: http://www.foodnetwork.com/recipes/alton-brown/pomegranate-syrup-or-molasses-recipe/index.html .