Lightweight wood for monitor wraparound

I am looking to make a crude wood/sound panel partial wraparound for my monitor to help with some audio recordings.

Been a long time since I did a bit of woodwork. Our local builders' merchants do custom cutting of wood etc

What is the next step up weight and quality-wise from balsa wood?

What type of wood should I use? I was thinking chipboard but perhaps want something a bit better quality but still cheap and not too light or heavy as it will be resting on the plastic areas of my monitor.

Some I have seen on Ebay: Birch Plywood 6mm, MDF