I've used Stutterbox in the past ([https://stutterbox.app/](https://stutterbox.app/)). Funnily enough it's supposed to make normal people stutter but is essentially just DAF without pitch adjustment. If you prefer pitch adjustment, there are a couple iPhone apps like "DAF Pro: Stuttering, Parkinsons" but they cost a few dollars. Not sure if they work in the phone's background, but I've just run them on my M1 mac and it's worked well. Good luck for your interview!