Try going on job interviews for jobs you have absolutely no interest in accepting, for two reasons. First of all, you'll get practice in speaking in that type of environment which can help if you go into it with the right mindset. Secondly, you can use it as a sort of troubleshooting opportunity if you will. Do you stutter as much when it's a job you don't care about? If not, then it's probably the anxiety of not getting something you want (or being rejected) because you stutter that causes you to stutter. If you still stutter, then it's probably something else. Either way, you can use it as an opportunity to figure out what if there's a specific situation or feeling you experience that makes it worse.