Printable Piano Key Diagram?

Hi! My 7 year old son has just started taking piano lessons but I do not have a piano yet. I am planning to get one, but in the mean time I would like to have something for him to practice with. I was hoping to find a site that has a full size printable piano keyboard. Like something that would print on several sheets of paper, I could print and tape together. Or, perhaps someone knows of a book or something that comes with one? Thank you in advance for your help!