I went to Southern Seaplane in New Orleans for my commercial ases add-on. They have a part 141 school and they offer both land and seaplane training, single and multi-engine. So I’m sure that they could help you out. They are very organized with many instructors and DPE on-site everyday. Go to their website and check them out and send them an email. They will get back to you with scheduling options very quickly. Price was very reasonable from my research.
I’ve been to other schools and scheduling a DPE was difficult to find dates, rescheduling due to weather, and aircraft maintenance. So I’d probably stick with something in the south that’s known for good weather.