I've posted a few times about Creve Coeur Camera, although I frequent their Springfield, IL store, not their St. Louis one. They're happy to have a film camera sent up from St. Louis, and their lab services are good quality and reasonably priced (okay they don't do $2 C-41 dev only, but you'll pay more for 35mm C-41 at wally world and only get prints and a CD back!) Their lab didn't bat an eye when I sent some Rollei IR400s through, and they had no problems with polyester based E6 as well. No problems with push/pull processing or return of my 620 spools, either.
They carry some slide film, a couple Ilford film emulsions, both in 35mm and 120. Small selection of Ilford papers, and some B&W chemistry and darkroom stuff (no enlargers, but they do have the stuff to develop 35mm and 120). They even have a lightbox or two at their counter, and a couple loupes for looking at negatives and slides. No Portra 800 but they do carry 400 and I think Portra 160.
I took in some 35mm C41 that my daughter had shot, and they were like "Whoa, normal film from you!" (I'm usually the E6 or B&W guy, not the color print guy).
If you're already in St. Louis, go ahead and check them out. They've got some used film cameras at the main store in St. Louis, I believe.
Oh, and +1 on the City Museum. It's awesome.