Try Paizo's Superstar submissions this year. Two of them were set at a side show. Also, Carnival of Tears has maps for that, if you're willing to buy a module or pdf.
I don't know how old school your Dungeon magazine collection is, but there is an adventure in an early issue (before #10 I think) titled: The Jingling Mordo Circus. I think there is a layout of the place in that one.