Where can i go to buy stencils stuff. so i can put fake tattoos on my arms but have them look real?

i know this is really early to be planning this but i don't care. so im thinking about being either the greed goddess Athena or Aphrodite for Halloween this year and i want to put swirls on my arms and legs. but im not a good artist. so does anyone know of any stencil stuff that i can put on my arms and legs that will stay but will wash off in the shower or if it lasts for a couple of days that's fine. thanks(: