Currently I'm reading Lee G Lovvet's book and found few helpful advices how to go around first feared sound. You can simply skip first letter or syllable and people either won't notice or care. Surely if you randomly say izza people might get confused at what the hell is an izza but if you order izza, double pepperoni, medium size please at the pizza place that's totally legit. Same works with amburgers, andwiches, urgers etc. Also according to the author 90 percent of stutterers do not stutter while whispering, you don't have to whisper the entire time you speak only when the block hits, once you get past the block you can return to your regular speaking voice. Also you can rearrange your thoughts. Instead of pizza, double pepperoni say double pepperoni pizza, your mind might be so focused at blocking letter P that once you substitute P with D it doesn't have enough time to follow. Or you can combine the methods. Also personally I've noticed that if type an imaginary keyboard sometimes I get too focused at remembering where the letters are it distracts my mind from blocking.