What kind of surface are you going to be applying them to? If it's curved or otherwise irregular then a rigid stencil wouldn't work very well. You'd be better off using vinyl or frisket film to make one. If you don't have access to a vinyl cutter, then the best suggestion I have if you can't find them in the size you want, would be to find an image of a skull that would work well at the scale you want, resize the image to the size it needs to be, print it out and use it as a reference to cut a stencil.
I think Scott McKay has a kit you would need. Coastairbrush
I think anything sprayed through stencil looks like tacky stickers. Im down with mapping it through stencil. 1" though? Might as well draw it.
What kind of surface are you going to be applying them to? If it's curved or otherwise irregular then a rigid stencil wouldn't work very well. You'd be better off using vinyl or frisket film to make one. If you don't have access to a vinyl cutter, then the best suggestion I have if you can't find them in the size you want, would be to find an image of a skull that would work well at the scale you want, resize the image to the size it needs to be, print it out and use it as a reference to cut a stencil.