Hi Kerry,
I don't have one of these so I'm shooting from the hip, so to speak
I would imagine using a PVC flange for a 4" duct would be pretty easy to find and adapt to the booth. Possibly a closet flange would work, with a 4" flexible, rigid or semi-flexible duct line. The booths fan may not be powerful enough to vent it through a certain length or bends, but a short straight run may be ok.
Now, according to Jason the instructions state that no additional venting be attached...so I'm not recommending this without consulting the manufacturer...cma