Okay so ive read about styrofoam

You basically cut out room for your transplants, and the styrofoam will float..
So you want to cut out a circular disk that will fit the 5 gallon bucket...

When the water level drops, the styrofoam will drop too, and when it rises the plant will rise...

I think that's a pretty flawed system though.. And personally if I were you, I would seriously just wait however long it takes to get your rockwool and hydroton (expanded clay pebbles).... I'm absolutely positive it will be worth the wait in the end...