Are you looking for something that you can whip out of a drawer or handbag that will occupy a child?
I was recently given a copy of a large-format activity book called Joseph Activities (ISBN 978 1 915 705 907). I really like this book as there are a variety of different activities from straightforward colouring-in, to spot the difference and mazes, as well as some more unusual puzzles that involve basic arithmetic and copying.