Although I'm not sure you could really achieve your nutritional needs with a 500-calorie diet, you could easily fashion your own. For example:
Breakfast: Scrambled egg whites with grilled peppers and onions, using 0-calorie non-stick spray, with one slice of light rye Wasa bread (approximately 80 calories if you stick to serving sizes and there are far more peppers and onions than egg)
Lunch: One of the Healthy Progresso Soups (anywhere from 50 to 90 calories per serving, which is 1/2 can) with another slice of Wasa (30 calories) and a wedge of Weight Watchers Swiss (30 calories) . . . for a total of 110-150 calories, depending on your choice of soup.
Dinner: 1/2 medium zucchini cut into strips to look like noodles, sauteed in 0-calorie spray with a little onion, garlic and mushroom (approx 50 calories) with 1/4 cup meatless marinara (30 calories for the brand I have, think Heinz) and 1/4 small can of clams (25 calories) . . . total of 105 calories
Snacks: a couple of rice cakes throughout the day (20 calories each for Fiorelli brand). You could even top one of the rice cakes with Babaganoush for flavor (20 calories)
I have quite a few days I stay at 500 calories or less, but I wouldn't recommend it for extended periods of time. It just doesn't give your body what it needs to stay healthy, and, if you restrict your calories too much, your body basically freaks out and takes energy from muscle, not fat.