Do you live near a smaller, independently-owned backpacking shop? If you can get to know the staff they might be able to contact their suppliers and special-order longer/larger gear and clothing for you. Many manufacturers make larger-sized versions of clothing and gear, but stores don't carry them because they don't have much demand. These stores are often willing to provide better customer service and order these for you.

Online stores will sometimes include larger/taller sizes in their "catalog," too. If all else fails, try manufacturer websites.

If you're handy, make-it-yourself might also be a possibility.