If you are opened to considering central Canada, I highly recommend Lake COuntry Airways:
Lake Country Airways: floatplane training, endorsements, float charters and rentals
I have done training with them, and very much like their way of doing things.
That said, "renting" a floatplane, and taking it somewhere is not a given. There are a lot of factors which make float flying much less certain that wheel flying. Remind yourself that EVERY place you take a floatplane to land it is NOT an airport, and very likely does not have the usual facility support, if any at all. Indeed, you can easily get floatplanes into places where even the most simple mechanical problem or accident becomes a very big deal. I know, I've flown in to take repair parts in, or to help get the wreck out.
Float flying is wonderful, but has a demand for skill and experience very much greater than the minimum skill requirements for the rating.