Cass Bonsai is in Edwardsville, a suburb of Saint Louis, about 40+ miles east into Illinois. Good Pla=e.
For Satsuki Azalea David Kreutz at Satsuki-en is a must visit. David is by appointment only, check his web page and give him a call.
The Missouri Botanic Garden is a must see if you have time. Not so much for Bonsai, but MBG is one of the oldest Botanic Gardens in the Midwest. some really cool stuff there, including a Buckminster Fuller Dome greenhouse. Looks Modern, even thought it is from the 1940s.