of you failed at contacting him contact twitter support team directly and maybe they will arrange something between you both and it doesn't have to be sold to you since it violate their service terms of use.
I have contacted support at Twitter two times, they're only responding with a auto-message saying that they're too busy at the moment but will contact me again when they have the time
you need to contact them and ask for it, maybe you can buy that )) .. send a twitter msg fist, if no response try to google the twitter name and find whether they have a website or not for the same name, if they have, u can contact them through the website
I've tried to do the same about two or three months ago. There was a user with no tweets, followers, wasn't following anyone, had the default background and user pic, etc. I sent Twitter a message saying this is using my brand name and it's an inactive account can you please free it up. They replied back that you can't always judge account inactivity or some similar canned message. I doubt they even bothered to look at the profile because it was clearly untouched after two years. Twitter just doesn't seem interested in helping with this unless you're a big celebrity being impersonated.
That's exactly what I've experienced. They still haven't contacted me, other than the two automated messages.