I'm afraid I won't manage to finish it in time.
I have something almost finished but it's quite awful.
In the meantime my husband came up with a better idea but I don't know if I can illustrate it - we'll see.
(Anyway, I'm writing this as a kind of note to self)
Update: So, I've decide to post it anyway (thanks to Laurel's encouraging note), but I left out the colours - it's a bit less awful that way.