I don't have an issue with choosing alternative sounds for the 'clicker' but I do think it is also a worthwhile challenge to create a positive association to that which he has become afraid. Go ahead and use alternatives in training but meanwhile.......

Isn't there a happy time, like chow mixing time, that you could go to the kitchen, click the clicker and mix up his food and click again before you set it down where he can chow down? Think classical conditioning. Think PAVLOV. Do the Ivan Pavlov thing but instead do it using the clicker that is the source of the sensitivity to associate it with the 'dinner bell'.

Once he associates the clicker sound to his bestest ever yummies... Conquer the fear? Can he do it?