Hi, Sory not sure how to answer this one as not sure of USA regulations or what fittings are available. I can't think of any reason why you couldn't add another toilet (toilette is French), but cannot suggest how to connect without seeing the layout of the existing waste or positioning.
I've came over to Florida two years ago and loved it. Did all the touristy things, Space centre, Universal, Everglades and ended up at Key West which was fantastic. Which part of Florida are you from?