Seems like they don't... I'm looking to order replacement mounting screws for the MBUS Pro sights and never get anywhere with email. It's been like that all year.
And I'm not even sure that they'd ship them to me anyways being in Washington, but trying to find out is like pulling teeth.
I emailed Magpul around a year ago about getting some spare MOE grip screws and got a reply back saying "sure thing, how many?", I answered back and never heard back from them again.