Go into any store that sells hunting stuff, even just a Walmart, and you'll find the license holders. They range from $1.50 to a couple bucks depending on the color/style/quality. It's not worth someone mailing you one--just stop in anywhere in WI and pick one up! (Says the guy who first hunted in WI last year and couldn't believe the size of those things!)
Doubt if I'll be stopping anywhere once I'm in Wisconsin. We'll be arriving late and hunting six days straight starting the next monring. MaybeI can find one on line.