Extending waists on cloth diapers?

I currently use Gerber Prefold Cloth diapers and snappis to fasten them on my nine month old daughter. However, I'm having a difficult time pinning the diapers because they are getting snug around her mid section. What I want to know is if there is a way to extend the waist without having to buy a whole set of new diapers. I'm on a tight budget and I really can't afford to buy new diapers. Any ideas would be greatly appreciated.