These are available from Rapid Education. This  ought to take you to a list of all of them. The most relevant ones they sell are:
52-7044 Time Clever Catch® £9.21
06-6522 Alternative energy Clever Catch® £9.21
06-6466 Astronomy Clever Catch® £9.21
52-7040 Physics Clever Catch® £9.21
The balls are inflatable and about 60 cm in diameter. They are covered in questions and are thrown around the classroom. The pupils catching them then reads out the question nearest their left thumb and either answers it themselves or someone else answers it. These are a US import and they do have a few questions about things like time zones that you’d probably want to cross out with a permanent marker. There are also blank balls available although with a permanent marker and a cheap beach ball you could probably do the same thing for less.