If you're targeting Dragon Con, I'm guessing you're somewhere in the southeastern part of the US, so I'll pass out a few useful links-

https://www.facebook.com/groups/RoboCommunity/ -This is the general robotics community page on Facebook, tends to be a bit US-centric but covers a wide range of stuff

https://www.facebook.com/groups/AtlantaRobotFightClub/ -Group focused on robot combat in the Atlanta, GA area

https://groups.yahoo.com/neo/groups/...QxMzEwNTA3MA-- -This is the Yahoo group for Robot Battles

Also, I put together a presentation recently that I gave at a local makerspace (Freeside- https://wiki.freesideatlanta.org ) which can be found here- http://nearchaos.net/RobotCombat101.rar It's focused around combat in the southeastern US and has a good deal of links to vendors that may sell what you're looking for.