Westside Airboats in the Davie/Weston area is just off the interstate (595) in Broward - if you don't mind dragging your hull across the alley.
Southern Enterprises is in Naples I think. I'm not sure what they actually build at their shop, but you may want to call them too.
cchardt rigs boats in Melbourne. Not an unreasonable drive. Scenic at least.
That's a start. I'm sure more options will come up from others too.
matt.