You can hit Exotica, bonita creek, ONG. There may be others but those have the most rare stuff.
One piece of advice is check the plants over really well before buying. Make sure they are in good health and not infested with bugs. I have bought a few rare plants and then get them home and realize they are covered in scale. Had an avocado tree with persea mites infect my grove also. Maybe take some neem oil with you and spray the plants before taking home.