http://wow.curse.com/downloads/wow-addons/details/shield-left.aspx
Found it in less than 2 minutes. Though, it is over a year old, so I doubt it still works.
Edit: This is the latest version (not sure how well it works with Wrath though): http://wowui.worldofwar.net/?p=mod&m=6421
Also this one is being updated: http://www.wowinterface.com/downloads/info11413-Shieldmonitor.html
Edited, Nov 17th 2008 7:42am by Caia