You can go to Lowes or Home Depot and get some coroplast, it is just like cardboard but made of plastic. You can divide the cage vertically or horizontally with it.
I dont even worry about it. Ive kept many hatchling chameleons in an adult sized cage with no trouble what so ever. Keep the potted plant off the bottom so the feeders dont hide (do this with adults anyway too) and the will find them just as easy. In nature they have no boundaries and find their food just fine. Not sure why people feel the need to baby these animals so much
Keeping the plant off the ground? I use anything from a bowl to the bottom of a plant pot. Anything that gets it just an inch or few off the bottom and doesnt have cracks so crix cant get under it.