That man's unpredictable. I used to get nothing but Lum Berries. However, on my current save file, he never game me one either.Don't worry about it.
http://bulbapedia.bulbagarden.net/wiki/Berry_Master
Bulbapedia doesn't give a phrase for Lum Berry...
I found a link saying BAD DATE is one to get a Lum Berry. Try that. However, it said Overwhelming Ninetales gets a Leppa Berry...I think if you don't get the password for the one-off berry, it's randomly selected.