Setting up power-off icon

I want to set up a large power-off button, with an icon, preferably on the desktop but on the panel would do. The ordinarily available one will not do because this is for someone with very poor sight and the ordinary power-off button is inextricably linked with lock screen. Well, I can't extricate it. I THINK I can manage the three other large icons that are needed on the desktop, but this one has stymied me. I could rephrase the question: how do I produce an icon that, when clicked, operates /sbin/poweroff. Jessie with TDE 14, installed from Slávek's repositories. Replacing a badly scammed Windows 7! Help!! Lisi