It would be difficult to give you direct advise but there are some criteria you may want to consider first.
What sort of sound are you looking for? You may want to get on the video sites and search the name of particular models to see what they sound like. make sure to visually check the video to see what they are actually playing. Some models can mimic a harmonica, some are more like an accordion or bandoneon. The Andes 25 has flutes instead of reeds.
What sort of range do you want? Twenty-six, thirty-two, thirty-seven on up to the Hammond. There are also bass melodicas and a few or one soprano model available range-wise. What role do you see the melodica fulfilling in your music?
Good luck in your search.