I can't find any way of doing it. If you right click the desktop, personalise, then display you can enlarge text on virtually everything except the toolbars!
However this might help but could be annoying in a way. Right click desktop, personalise, then select Ease of Access on bottom left. Select 'start magnifier'. you get a small pane up, or if not showing click on magnifying glass or icon on taskbar. Select views then 'docked'. This will dock the magnifier to the top of the browser and you can shorten it to your needs. Now that dock will magnify to your settings wherever the mouse pointer is. On the taskbar you could 'pin' the icon so once you've finished with magnifier just right click the taskbar icon and select close window. You could also click on the magnifying glass, which opens the small magnifier pane and click on the 'X'.
When you need it again simply left click on the icon on the taskbar.
That's the best solution I can find.