Merde! No Celery! Sacre Bleu! Infidel!
I have some celery seeds. If you go that route, be very conservative on how much you use, especially if you saute the seeds with the rest of the veggies. I find that to many celery seeds give a very bitter flavor.
Years ago, I found some dried celery flakes with the rest of the spices. While that can a definite celery flavor, I don't remember the cost, and most likely, a bundle of celery probably costs about the same. If you have a food dehydrator, you could dry your own.
Suzie, it looks like you have a nice, tasty soup. Have you thought about adding just a little bit of thyme, sage, and rosemary? Those are my three "go-to" herbs that I put into just about everything. If I were to make this soup at home, I would dice up the skin and cook that with the bacon, to give it a caramelized chicken flavor. If I were making it at work, I'd saute the bacon, remove it from the pan, jack the heat up as high as it would go, let the pan get good and hot, then add diced raw chicken and caramelize that. However, your method will still yield an unbelievably tasty soup.