As an initial trial I did the same basic thing that Saritastar suggested. Only difference was that I used wire mesh to separate them. I doesn't burn and allows the heat to go all the way down and threw the two sides evenly. It seemed to work perfectly. It is simple and cheap. I used some scrap that was in the garage. Cardboard boxes can be had for free and can be turned into a lot of stuff. My first brooder was four boxes, wire mesh, and Tuct tape. It was warm in the middle with two progressively cooler areas for the chicks to explore. As they got older they moved away from the heat lamp as they wished. This way they can control how much they need/use. I even put in perches so they could perch when ready.
Older on the left, younger on the right.
Even the little Silkies did fine with the set up.
Be creative and you can find a solution.

Older on the left, younger on the right.



Even the little Silkies did fine with the set up.
Be creative and you can find a solution.