cannot uninstall SupportAssist without the msi

The MSI for a previous working version has been deleted and replaced with an MSI with the newer (I presume the newest version. The newer version did not complete install, just said there was a problem, so reboot and try again..

So at this time I have an old version that does nothing and an MSI for a newer version where the original should be and won't allow the older version to be uninstalled, which means the newest version won't install either.

Many seem to have this problem, but cannot find any solutions yet.

Is it possible to get an msi for SupportAssistx64-3.4.0.200.msi or is there a way to uninstall without an MSI?