I think DrDamage does what u want, doesnt have the mana bar as on your posted pic, but it's able to shown on action bar buttons how many of certain healing spells (and other spell/melee/etc) you can do with the amount of mana you have.
http://www.wowinterface.com/download...-DrDamage.html
Edit:
newer version here if you're not afraid of testing alpha/beta versions
http://www.wowace.com/projects/dr-damage/