WM makes 7' long bagsI don't know if bags like Western Mountaineering or Feathered Friends can accommodate you with anything more than what they have available in long versions of their bags, but you may want to check these guys out:
https://www.phdesigns.co.uk/customsleepingbags.php
These guys make a bag for people up to 7' tall and from what I've seen, PH Designs bags are well reviewed, but I don't have any personal experience with them.