Do you still have "Black and Blue Too" installed? Have a look at that, see how it's done in there...
Within the <LIST> block, you need an entry along the lines of: "<Entry Name="InPlaceFindToolbar" Bitmap="List_InPlaceFindToolbar.png" NumberImages="1" .... "
Next, complete, integrated skinning tip...
Some things, like quick find, tabs etc., get added to MC over time as new features. MC helps "pre new feature" skins still work by adding the required parts to a "Default Skin Items" folder found in the installation directory "Data" folder.
In there, for example, you can find tabs.
If you make a skin and don't include images and xml data for tabs, MC will still show them, taking them from this default skin items folder.
The xml needed to draw these default items is shown in the included xml in this folder.
If any of these default items are explicitly specified in the actual skin directory, then those are used in favour of the default skin items ones.
It's always best to specify your own as the defaults provide the fucntionality, but rarely fit with the rest of your skin.
Hope that helps a bit.
-marko