Something like this:
I drew some idea down but couldn't think of an appropriate net, then with a little bit of help I think I came up with the right kind of idea.
I tried a mock up with paper,it was very rough but seemed to work.
I then drew up a similar net on the computer but as I was doing it I thought there was something not right but I printed it and put it together anyway to see.
Something about rounded sides are not right, I'm not sure if it'll be different when I make it with card cos it'll be more stiff but I need to alter it. I know that the bottom cirle needs a flap on it to stick to the other side but I'm still not sure if it's folding correctly as it is.