The brand I've seen most often in stores for Whole Wheat Pastry Flour is Bob's Red Mill -- they have a store locator on their website where you can look for a specific product which may be worth a try.
Personally though, I don't usually purchase whole wheat pastry flour and have had success substituting white whole wheat flour (still 100% whole grain, just made with a different variety of wheat) which I always have on hand. I find that it is milder than regular whole wheat flour and the flavor and texture difference isn't as drastic compared to white flours. I know Gold Medal Flour, King Arthur Flour (my personal favorite), and even store brands often offer white whole wheat flour now. All that said, I don't tend to make very fancy or delicate pastry-type recipes. But for everyday baking, I would definitely use the white whole wheat as a substitute for whole wheat pastry flour.