Thank you Rare Bird Finds for turning me onto this nifty soap idea.
CityBird sells these for $6 on Etsy. Hurry though, there’s only one left on this sale. They do bulk and custom orders in case you want to direct hapless tourists in any area of the country. Quoting from their site:
Our original product (and still a favorite!) is our translucent city map soap currently available with detroit, chicago, new york and brooklyn maps. each soap is handmade from a vegan base, scented with all-natural scents, and tinted with natural, vibrant colors. the map image is embedded in the center of the bar and will stay until the soap is gone.