Just get a good quality Vinyl Sticker (Bumper sticker) and pass it through a 3 hole punch. You can make as many as you need, in any color you prefer. They hold up nice. You can always get these quality stickers for free from your local radio station.
When it came time for markers on my first guitar I was going to inlay a lighter colored dowel in a 1/4 inch hole drilled in the neck. But instead I found an eraser pen with a 1/4 inch white eraser. So I drilled 1/4 inch holes, shoved the eraser into the hole and cut it off flush with a razer blade.