Prank.. need help.....?

Alright, im only in 8th grade.. end of the year is coming up, on the 16th. The seniors at the highschool had a plan to buy 10,000 bouncy online and throw them on their last day. because the janitors cannot sweep them up easily. They were caught and it didnt end up happening. but me and my friends we planning on doing the same only with alot less. I don't know if we have the time to buy them online. Does anyone know where i can buy bags of bouncy ??