removing a burred over caliper bolt

[batfink]

My friend tried to change his brakes today and managed to burr over the 13mm bolt to the caliper cover.
What tool can he buy to remove it as its pretty fecked. There are the sockets with the bristles that grip the damaged head but I cant find where to buy one from and i've been told they are not very good?

Any suggestions? If anyone has a welder in local area then that would be a solution to get another head one so i can now do it properly. :lol:

[batfink]

its just a standard run of the mill hex bolt.