Cider Donuts in St. Louis?
I just did a sweep of donut spots for my new blog: www.stlchow.blogspot.com and did not come across any cider donuts. Last time I had some I was outside of Ann Arbor, MI on an apple orchard. They were very good and I just assume that they added some cider to the batter. The glaze was what really made these ones, though.
I met a lot of very nice owners of donut shops and you could probably put in a request and see what some donut stores say. I'd try talking to John and John Donut on S. Broadway and see if he'd have any interest.
Check out the post on donuts for more info.