Does anyone know how to make a rock tumbler?

okay so i need to make seaglass in like 3 days for a science project. i was wondering if anyone knows how to make a rock tumbler that would be quick and easy to make or if theres any place with a cheap rock tumbler i could buy. i would put the glass in the tumber and fill it with water and i need something im only 14 so i need something easy to make.