It's possible to get it yourself, but most likely hard.
First of all, it's good to try reseting password, so you go to "Forgot password" and type the username. If prompts "You can use the information associated with your account." and below that is a part of email, you can speculate how email looks and find sites with leaked passwords on haveibeenpwned, then download DBs and try logging into the account. If "You can use the information associated with your account." doesn't prompt, maybe try using proxy.
If the username has a connected website in bio, it should be easier. First, look on connected site for emails then again, go to "Forgot password" section and type emails. If one of them works, it would ask you for your username, you type username of your desirable account.
That's all I tried really. You have to be very lucky tho.
PM me the name, maybe I can help