I've also been frustrated at the lack of good tortialla shells available, and came up with this recipe, it tastes great, but a bit on the hard side. I ran it under water before flatting out, and that seemed to help.
• 5 cups whole wheat bread flour
• 3/4 cup olive oil
• 2 teaspoons salt
• 1 1/2 cups boiling water
• Whole wheat flour for rolling
1. In a large bowl, stir together 1 cup all-purpose flour, the whole wheat flour, and salt. Rub in the olive oil by hand until the mixture is the texture of oatmeal. Make a well in the center, and pour in the boiling water. Mix with a fork until all of the water is evenly incorporated. Sprinkle with a bit of additional flour, and knead until the dough does not stick to your fingers. The dough should be smooth.
2. Make balls the size of golf balls, about 2 ounces each. Place them on a tray, and cover with a damp paper towel. Let stand for at least 1 hour, or up to 8 hours.
3. Heat a griddle to 375-400. On a lightly floured surface, roll out a tortilla to your preferred thinness. Fry one at a time. Place on the griddle for 10 seconds, as soon as you see a bubble on the top, flip the tortilla over. Let it cook for about 30 seconds. While waiting for those tortillas to form bubbles, quickly flatten next 2-3 balls, then roll out after flipping the tortillas on the griddle. Repeat until all of the balls have been cooked. Tortillas can be refrigerated or frozen.
4. YOU ONLY NEED TO FLIP THEM ONCE. COOKING TOO LONG WILL LEAVE THEM BRITTLE.