I don't know of any shops or kiteboarding schools in Missouri personally but found the following from a net search:
Gulfport Windsurfing
City: Gulfport
State: MO
Zip:39507
Phone: 228-864-7517
If Florida's Panhandle is doable for some weekends you would do well to hookup with some experienced instructors there if other better options closer to home don't show up. Mark Rush with
http://www.emeraldcoastkiteboarding.com/ comes to mind in Panama City.
Regarding trainers, you could go with many different 1.5 to 3 m foil kites for this purpose. I would check with Rush or the outfit in Gulfport to see what they have and relative pricing. You may be able to find one used on Ebay or ikitesurf as well.
I am not a huge fan of spending a ton of time on trainer kites alone. I feel by all means start with a trainer to develop kite control, basic launching, landing, relaunching, etc.. I feel moving on to a small inflatable kite, say around 3 to 4 m will provide some valuable insight on how full sized LEI traction kites behave than might be imparted from a trainer foil. I don't mean to move from a trainer to a full sized LEI without an instructor either, not a good idea. Your instructor will provide trainer kites for a fee of course so there is no imperative need to get one yourself unless you want to try to reduce your time in instruction.
There may be some operations in Alabama as well but again, I have no personal knowledge of any. Be sure to interview your prospective instructor to improve the odds you get what you need and are paying for. Some ideas along those lines appear at:
http://fksa.org/showthread.php?t=937
Let us know how things are going for you.