I would use escrow.ms
But no way am I giving you a username when you don't even seem like a legitimate buyer who's ridiculously sketchy,
Every account seller will never provide account name first before he'll get his money because of the risk getting neg REP'ed, They will only show the username when escrow got the money or you pay them first, I saw that on several threads that they never display names first and they have the reason to do so like I said before.