Retrieving a CommandbarPopup in Visual Studio to add buttons has always been tricky. There are incorrect ways to do it:

PRB: Performance problem of DTE.CommandBars[name] for CommandbarPopups in Visual Studio 2010
http://www.mztools.com/articles/2011/MZ2011005.aspx

BTW, I have updated this popular article to avoid that performance problem in VS 2010:

HOWTO: Adding buttons, commandbars and toolbars to Visual Studio .NET from an add-in
http://www.mztools.com/articles/2005/MZ2005003.aspx

and there are correct ones:

HOWTO: Locate commandbars in international versions of Visual Studio.
http://www.mztools.com/articles/2007/MZ2007002.aspx

HOWTO: Get a CommandBar by Guid and Id rather than by name from a Visual Studio add-in.
http://www.mztools.com/articles/2011/MZ2011004.aspx

And now Visual Studio 2010 introduces a new one, which is correct, but doesn’t work in international versions of Visual Studio 2005 and 2008:

INFO: menuCommandBar.Controls[“Tools”] works in international versions of Visual Studio 2010
http://www.mztools.com/articles/2011/MZ2011006.aspx