please do not leave a duckling with him, or one single female. He does need companionship, but 1 drake can easily overbreed and exhaust a female, sometimes causing injury or even death. The correct ratio is 4 or 5 female ducks for every 1 drake. If you were to get one drake, it is likely they will fight, I believe muscovies are known for being a little aggressive? Not certain on that, but I think more drakes would be risky.
If you are able to get a few ducks for him, that would be good, but try and choose a breed that isnt too much smaller, I guess female muscovies? I don't know a whole bunch about this breed, I only keep pekins/aylesburys myself, but definitely more than just one female...