I looked on Max Fisch and didn't see any prominent providers based in St. Louis.  This doesn't exactly answer your question, but it looks like Missouri has a fair number of lifestyle groups, so I'm posting this link in case it is of interest to you.  Hopefully, someone else here will know of a sensual dominatrix who can make your "gateway arch".

Sensual Domina!

Hi I reside In SD but am from STL I will be there to party and play Aug 19th-25th if your looking for a Nubian Goddess to explore with then read my ad I povide sensual to strict BDSM Play... If you like it I love it!

I will be fully equipped with toys for KINKY fun!
I can be the perfect companion or your Sinful Domina just ask!

[email protected]

Goddess Amoni