Raise money for a debate team

You're the advisor for the debate team and you want to get the students a good deal on shirts they can wear to competitions. Thing is, the deal doesn't last forever and you can't pay the money out of pocket yourself. You need to collect the money from the team members and you need to do it fast. You know they'll forget to bring the money in, so you need another solution. Something they can use to pay you immediately.