My DH is 6'9".
Can he go with you to a store to try things out? If you go to one of the expensive baby stores that carry everything, you might get ideas. You could always look online then for a better deal. The carriers with the broader straps (like the Ergo) and the ones that look like hiking packs (with the metal bar) seem to be biggest. I'd stay away from the cheaper thin strapped carriers, they're a pain to use even for a normal sized person. I saw one in a used store by Theodore Bean, it was leather and comfortable and really big. (I skipped it because I wasn't sure about the leather getting hot for a summer baby.)
I'd suggest getting baby equipement with room to grow for your little one. You baby's probably going to be tall. My son's dad was 6'5, my son was 22 1/2