Official non-platform SDK download location for msizap.exe
Thanks to a heads up from someone who read my previous post about msizap.exe, I am happy to be able to point to a download location where you can get msizap.exe (along with a GUI-based front end to make it easier to use) from a Microsoft KB article - http://support.microsoft.com/default.aspx?scid=kb;en-us;290301. This package contains an MSI that installs the tool, but it works correctly if you just extract the msizap.exe file and optionally the msicuu.exe UI wrapper. Note that the setup package is branded for Microsoft Office, but it is a generic Windows Installer tool that will work correctly for any MSI-based product.
Hope this helps (it definitely helps me - thanks to Martin Hueser for the heads up!)