Try looking here
www.tomiki.org , it is the Japan Aikido Association/USA , they list competitions regularly....The last major tournament was at the Arnold Classic, Columbus, Ohio....
http://homepage2.nifty.com/shodokan/en/index.html , this is the Shodokan Homepage...they have quite a bit of information, rules and such....
I believe the US National tournament is in New York this year and the International Tournament is in Vandalia, Ohio next year...
If you research Shodokan Aikido, or Kenji Tomiki, you will find that the it is not so much different than that of Aikikai Aikido...just more to the point...
Clark Shihan is correct, Tanaka Sensei and Nettles Sensei are located in Denver, Colorado...his email is
Nettles@Tomiki.org...
For those who refuse to acknowledge tournament or sport Aikido, forgive them for they know not what the are missing out on.....