I'm planning on making a cornbread stuffing (likely one of the NYTimes' recipes) for a potluck Thanksgiving. (e.g., stuffing will cooked outside of the turkey) Unfortunately, all of the recipes require celery. I'm allergic to celery and would like to make a portion without it for myself. What can I substitute for celery that provides the same flavor and texture? Celeriac and celery root are a no-go, and jicama and lovage aren't available where I live. 
You don't need to substitute anything, you can just leave it out. I've made both regular and cornbread stuffing with and without celery and I've never felt it was missing anything without celery, in fact I personally prefer it. Celery will release moisture as it cooks, I've found that I can compensate for it by adding a small amount more stock or water at the beginning. If you want to replace the texture element then I'd suggest chopped peppers, sauteed or roasted to partially cook them as if you add them raw they won't always cook through in time. Other options are apple and onion, although they are stronger flavors that may interfere with the result you want. 