You can do an easy one with just a slat of wood (I love ash for that), make it even in thickness and just use pyramid kind of design for the width of the bow. Make the bow long enough so that the limb won't be to much stressed out and glue an handle.
But, there is an easier way that could save your Christmas, instead of wood use a narrow PVC pipe that you can find at home depot drill a hole at each end to put the string, you can use pipe insulation foam and tape to make the handle, and you can spray pink the bow. There was an article in TBM a year or so ago. If you are interested PM and I'll try to find the article to give you more details.