This component uses the same setup as the Navbar User except for the event name it listens to.
Just add the following tag to your UserShowListener definition in the services.xml and you're good to go:
<!-- services.xml -->
<!-- ... -->
<service id="my_admin_bundle.show_user_listener" class="%my_admin_bundle.show_user_listener.class%">
<!-- ... -->
<tag name="kernel.event_listener" event="theme.sidebar_user" method="onShowUser" />
</service>