The command I posted above can simply be added to a toolbar button (and again, I recommend putting the button under a menu rather than directly on the toolbar)?
<?xml version="1.0"?>
<button backcol="none" display="both" label_pos="right" textcol="none" type="menu">
<label>Attribute Changer</label>
<icon1>#setattr</icon1>
<button backcol="none" display="both" textcol="none">
<label>Attribute Changer</label>
<icon1>#setattr</icon1>
<function type="normal">
<instruction>FileType CONTEXTFORCE CONTEXTMENU {D3F9A525-8824-497A-BE36-B23E22F141FC}</instruction>
</function>
</button>
</button>