I found a cute picture online and printed them to size of the clock with out overlapping the numbers...well too much. 
It's easy to just pop open the plastic cover and reveal the cardstock that is the numbers. Cut around the image, and then a slit down the middle to fit around the clock hands.
Set into place and taped where it looks right.
Oh, and take a sharpie to match up the numbers if you go over them a little.
Pop that plastic back on, and there ya go!

