The Bumps are great for java look and feel, but...
They don't suit the windows look and feel at all.
In the Toolbar code their is still the code for the Grip.
The request is use the appropriate grip/bump honouring the
current look and feel. I know that the proper way to do this
would be to go through the ToolbarUI, but here's the intermediate
solution that i used. It gives the Toolbar a grip or bump on startup
depending on the current l&f, it cannot be changed during runtime.

From Toolbar.java:
    /**
     * When Toolbar is floatable, ToolbarGrip is added as Grip as first toolbar
component
     * modified by Michael Wever, 28/4/01, to use l&f's grip/bump.
     */
    void addGrip() {
        if (floatable) {
            //ToolbarGrip dragarea = new ToolbarGrip();
            /** Uses L&F's grip **/
            String lAndF = UIManager.getLookAndFeel().getName();
            JPanel dragarea =  lAndF.equals("Windows") ?
            (JPanel)new ToolbarGrip() : (JPanel)new ToolbarBump();

            if (mouseListener == null)
                mouseListener = new ToolbarMouseListener();

            dragarea.addMouseListener(mouseListener);
            dragarea.addMouseMotionListener(mouseListener);

            add(GRIP, dragarea);
            addSeparator(new Dimension(4, 1));
        }
    }

My full Toolbar.java is also attached.