I imagine that you're obligated to turn the car in with the factory rims at the end of the lease. If you could swing it, just hold on to them -- you'll be able to sell the new rims at lease end to someone else I'm sure.

I visit South Florida quite often and although I can't give any specifics, all I can say is that if you can't find a place that sells wheels down there, you aren't looking very hard. Man, that place has to be the custom wheel capital of the world (or maybe second place to California, I imagine.)