Good place to start is by sending out press releases and newsletters as soon as you can to your current sponsors. You should also have your leaders set up presentations for your town council/school admin/board of education. You also have plenty of time left to do small fund raisers which can quickly add up.
For example - car washes this time of the year are a good idea because the weather gets a bit warmer and people want all the salt cleaned off their cars!
You may also consider having students pay for the travel/hotel rooms themselves. If this isn't as easy for some students, they can try setting up fund raisers like bake sales to offset some costs.
Hope that helps. Good luck!