I would suggest you ask your local division if there is one.
Also keep a sharp eye open to the upcoming invasion forum thread (http://www.toysoldiersunite.com/forums/upcoming-invasions) for any invasions at the cons in your area. If there aren’t any, you might use this forum thread to post your intentions and then you can see if there are any takers.
Just be aware that getting several soldiers together is, as is so often remarked, like herding cats and that success in not always guaranteed. But just keep it up and you’ll succeed one day.