It's not your job to run around like a loon finding every name under the sun then presenting them to His Highness for veto, you know...
Tell him quite cheerfully that you will be making a list of, say, 10-15 names to choose from. So far, it looks as if only your names that you've found and like are on the list. So if he doesn't start thinking and putting in some legwork of his own, then he will have no names of his own choosing on the list :)
If you do get to the point where it's D-day and he's saying no to everything, then that does not mean that he will get to dig his heels in and get the only name he's prepared to accept. Ohhhh no. What will happen, if you feel he's really not contributed to the discussion and is being obstructive, is that both he and you will veto, say, the two names you dislike most, and the rest will go into a hat.
Once again, point out that if it's your names on the list, then your names will be going into the hat... not his.
TLDR: he gets into the spirit of it or he gets very little say :)