there is no spell, you make it yourself.
find a branch [arm length] and whittle it into a wand, adding any decoration of your choosing. you could also buy it if you wish, this way you add more of a personal touch. once you have your wand bless it in a ritual. [if you bought the wand cleanse and charge it with your energy] say a little something to your deities, then leave it on the altar to be blessed. like with most magick tools you either make or buy it, but it doesn't become your tool until you bless it. when i dedicate my tools i put a drop of oil on it, pass it through some cinnamon incense and say a little chant.