Found this tasty recipe online at Diabetic Living, and there's more sandwich recipes at the link below
1 4 ounce fresh portobello mushroom
1 tablespoon balsamic vinegar
1 teaspoon olive oil
Dash ground black pepper
1/4 of a medium yellow or red sweet pepper, stem and seeds removed
1/4 cup chopped tomato
1 large whole wheat pita bread round, halved crosswise
8 fresh spinach leaves
8 small fresh basil leaves
1/3 cup crumbled feta or goat cheese (chevre)
1. If present, remove and discard mushroom stem. If desired, remove mushroom gills. In a small bowl, combine balsamic vinegar, olive oil, salt, and pepper. Gently brush half of the oil mixture over mushroom and sweet pepper.
2. Place mushroom and pepper on the rack of an uncovered grill directly over medium coals. Grill for 10 to 12 minutes or until the vegetables are lightly charred and tender, turning frequently.
3. Meanwhile, in a medium bowl, combine the remaining oil mixture and the tomato; toss gently to coat. Cut grilled mushroom and pepper into bite-size strips. Add mushroom and pepper strips to tomato mixture; toss gently to combine.
4. Open pita halves to create pockets. Line pita pockets with spinach and basil. Fill pita pockets with grilled vegetable mixture. Sprinkle with cheese. Serve immediately. Makes 2 servings.
Source: Diabetic Living Online